Learn React - React Crash Course 2019 - React Tutorial with Examples

So you’ve probably heard that there is big hype for React these days. You’re curious to find out what it is and why it has a high adoption rate. And you want to quickly learn how to build a simple page using React. If that sounds like you, this post is for you.

So you’ve probably heard that there is big hype for React these days. You’re curious to find out what it is and why it has a high adoption rate. And you want to quickly learn how to build a simple page using React. If that sounds like you, this post is for you.

If you prefer learning by videos, watch my React tutorial on YouTube; otherwise, continue reading.

What is React?

In my earlier post, I explained that **React is a lightweight library for building fast and interactive user interfaces. **Unlike Angular, which is a framework (or a complete solution), React is essentially a ‘view library’. It only takes care of the view or what is rendered in the DOM. It doesn’t have an opinion about other aspects of an app such as routing, calling HTTP services, etc. For those concerns, you need to use other libraries. This means you get the freedom to choose the libraries that you’re familiar with or prefer.

React Components

Components are the building block of React apps. A component is a piece of UI. It has data and describes what that piece of UI should look like. When building React apps, we build a bunch of small, independent and reusable components and compose them to make complex UIs. So every React app is essentially a tree of components. If you’ve worked with Angular 2+, this should sound familiar.

A Real-world Example of React Components

Imagine you want to build a web application like Twitter. Head over to Twitter’s website and you’ll see various pieces like below. We can implement each of these pieces as a React component.

Our component tree in this example could look like this:

  • App
    Components can include child components. For example, the Feed component includes several Tweet components and each Tweet components has a Like component. So, our component tree could be extended to something like this:
  • App
    We can re-use this Like component (or any other components in the tree) on different pages or even in different applications.

A component is typically (but not always) implemented as a JavaScript class that has a state property and a render method. State includes the data that we want to display. The render method describes what the UI should look like.

Setting Up the Development Environment

There are a few things you need to install to get started.

First, head over to nodejs.org and install Node if you already don’t have it on your machine. We don’t need Node to build React apps. We only need one of its tools (Node Package Manager or NPM) to install React and other libraries. You’ve probably used NPM before.

Second, you need a code editor. Feel free to use any editors you prefer. My preferred editor is Visual Studio Code/VSCode which you can get from code.visualstudio.com

Now, open up the Terminal on Mac or Command Prompt on Windows and run the following command to install **create-react-app **package. We use this package to bootstrap new React apps:

npm i -g [email protected]

Make sure to use the same version I’m using here even if there is a newer version available. I just want to make sure you can follow this tutorial all the way to the end.

If you’re on a Mac and haven’t configured the permissions properly, you need to prefix this command with sudo: 

sudo npm i -g [email protected]

Creat Your First React App

Now, type the following command to create a new react app:

create-react-app my-app

This command will create a new project with all of the required dependencies. It’s the fastest way to get a React app up and running with zero-configuration. You don’t have to configure Webpack, Babel, and other tools as create-react-app takes care of all of them.

Now, go to the project folder and start your React app:

cd my-app

This will start a development web server on port 3000 on your machine. It’ll also launch your browser navigating to http://localhost:3000. You see your first React app here.

Project Structure

Let’s see what we have in this project. We have 3 folders:

  • App
    Open up **package.json. **Chances are you’re already familiar with this file. If not, package.json is like an identification card for a project. It includes the project’s name, version, dependencies, etc.

Note that under dependencies, we only have 3 dependencies:

  "dependencies": {
    "react": "^16.4.1",
    "react-dom": "^16.4.1",
    "react-scripts": "1.1.4"

In reality, there are several other dependencies behind the scene that you don’t see here. We need

  • App
    The beauty of create-react-app is that it hides all these from us. So, we never have to manually configure all these tools which can sometimes be a pain in the neck. So, you can get started in a matter of seconds.

But what if you want to customize the configuration for these tools? Well, you’ll need to “eject” from create-react-app. You simply run:

npm run eject

And create-react-app will then add all those dependencies to package.json. It’ll also create a couple of additional folders in your project where you can see the actual configuration and customize it.

Remember: Ejecting is a one-way street. Once you do it, there is no way to go back to that clean configuration in package.json.

Hello World!

Now, delete all the files inside of the **src **folder. We’ll write all the code from scratch. Create a new file called **index.js **and write the following code:

import React from 'react'; 
import ReactDOM from 'react-dom'; 

const element = <h1>Hello&nbsp;World</h1>;


Save the changes. Here we have Hot Module Reloading (HMR). That basically means that whenever we change any of our files, our React app will automatically restart in the browser. We don’t have to manually refresh the page. Switch back to your browser, and you should see the Hello World message on the page!

Analysis of the Code

Now, let me explain what is going on here.

On the first 2 lines, we are importing a couple of React objects from their corresponding module.

import React from 'react'; 
import ReactDOM from 'react-dom'; 

Modules are introduced in ES6 or ES2015 which is a modern version of JavaScript. With modules, we can modularize our code into multiple files. Instead of writing all the code in one gigantic file, we split it across multiple files so our code is more maintainable. We call each file a “module”. Then, we can import one or more objects from a module and use it in another module.

On line 4, we are defining a constant (which is another new feature in JavaScript) called element. A constant is essentially a variable that cannot be re-assigned. In the old days, we used var.


Note the value of the element constant. It’s neither a string nor HTML markup. This is what we call a JSX expression. JSX stands for JavaScript XML and it’s an extension to JavaScript. We use it to describe what the UI looks like. We’re all familiar with the HTML syntax, so we use the same syntax in JSX expressions but there are additional features available to us for dynamically rendering data.

Now, obviously, browsers don’t understand this new syntax and chances are they never will. So, we have to run this code through a compiler (Babel) and convert it into something that browsers can understand. The result of compiling that code will be something like this:

var el = React.createElement(
  'Hello World'

We could write this code by hand to describe the UI (in this displaying “Hello World” using an H1 element). But as you see, writing code like this is tedious and error-prone. Plus, it’s hard to figure out what the UI really looks like when dealing with complex markup with nested elements. It’s much easier to use a JSX expression:

const element =&nbsp;<h1>Hello&nbsp;World</h1>;

React Elements and Virtual DOM

Now, the value of this element at runtime will be a React element which is a plain JavaScript object that represents a DOM element. It’s not an actual DOM element. It’s just a plain JavaScript object that describes that.

So, React keeps a lightweight representation of the real browser DOM in memory which is called the Virtual DOM. Whenever the data in our application changes, a new React element is created in memory. React will compare this element with its previous version, it figures out what data is changed, then it’ll reach out to the DOM and update specific elements to match the Virtual DOM.

Say Goodbye to DOM API

So, this means, in React apps, we don’t have to work with the DOM anymore. You never have to assign IDs and classes to DOM elements, query them, manipulate them, attach event handlers, etc:

var element = document.querySelector('#course');

We only work with React elements and components. We change the data or state of our components, React figures out what is changed and it’ll automatically update the DOM to match the state.

Rendering React Elements

Finally, the last line of our code:

ReactDOM.render(element, document.getElementById('root'));

Here, we’re using the ReactDOM.render() method to render this element in the DOM. Where in the DOM? Inside the element with the ID ‘root’. Where is this? Open /public/index.html. In the body section, you should see a div like this:

<div id="root"></div>

This is the container for our React app. In this example, we’re rendering a simple React element (h1) in this container, but in a real-world app, we’ll render a component. This component is called the root component and it wraps the entire app. It is on top of a tree of components. With this tree, we can render a complex UI in the DOM.

Your First React Component

Earlier I told you that components are the building blocks of React apps. But where is a component in this example? We haven’t defined one yet.

As I mentioned before, a component is a piece of UI. On this piece, we can have a single element (like an h1 element), but quite often we have a complex markup. That is the whole point of a component. We want to break down a complex UI into a bunch of small and maintainable components.

Now, let’s build a simple component.

Inside the **src **folder, add a new file: **counter.jsx. **You could use the **js **extension, but if you’re using Visual Studio Code, when you give a file the **jsx **extension, you get better syntax highlighting and code completion.

Type the following code and then I’ll break it down for you:

import React, { Component } from 'react'; 

export default class Counter extends Component { 
   state = { value: 1 }; 

   render() { 

Analysis of the Code

Once again, on the top, we’re importing the React object from the ‘react’ module. But, we’re not using that object anywhere in this code. So why do we have to import it? Earlier I told you that our JSX expressions get compiled to calls to React.createElement(). That’s why we have to import React on the top.

Next, we’re defining a class called Counter and exporting it. The objects we define in a file (module) are private or invisible to other modules by default. When we export them, other files (modules) can import and use them. Every module can have a default export. That is the main object that is exported from that module.

This class has a state property which holds the data that we want to display.

The render() method returns a JSX expression which is essentially a React element. Note that here we are using curly braces in our JSX expression:

<div>{ this.state.value }</div>

Whenever we use curly braces in a JSX expression, we can pass values dynamically. In between the braces we can write any valid JavaScript expressions. An expression is something that produces a value. We can write an expression like:

{ 2 + 2 }

So, 4 will be rendered in the DOM. Or, we can call a function that returns a value:

{ this.getValue() }

Using a Component

Now we have a component that renders the value of a counter. In this example, we’re using a single div. In a real-world scenario, we could have some fairly complex markup with nested elements and Bootstrap classes to make our app look pretty.

Let’s use our new Counter component. Open up index.js, import the Counter component on the top, and then modify the last line to render the Counter component instead of the element we created earlier:

import Counter from './counter'; 
ReactDOM.render(<Counter />, document.getElementById('root'));

See how we have used our Counter component? It kind of looks like we have extended the HTML vocabulary. We have encapsulated the concept of a counter behind an element like . Note that in JSX, if there is nothing between the opening and closing tags, you should use the self-closing notation.

Save the changes. You should our counter value displayed on the page.

Handling Events

Now, let’s take this to the next level and add a button to our Counter component. Whenever we click this button, the value of the counter gets incremented. So, back to **counter.jsx, **modify the render method as follows:

render() {
   return (
      <button onClick={() => { console.log('clicked'); }>Increment</button>

A couple of things to note: we have surrounded our JSX expression with parenthesis for breaking them down into multiple lines. If you don’t put parenthesis here and have a return keyword by itself on a line, JavaScript automatically inserts a semicolon after the return. So, nothing will be returned. To fix this issue, we have to wrap our multi-line JSX expressions with paranthesis.

Here, we have set the onClick attribute of the button to an expression. This expression is an arrow function. If you’re not familiar with them, be sure to read my post 4 Modern JavaScript Features You Should Be Using Now.

With this code, whenever we click this button, we should see a **clicked **message in the console. Save the changes and try it for yourself.

Updating the State

So, we got the button to do something when we click it. Next, we need to increment state.value. In React, we don’t update the state directly. In other words, we should not write code like this:


You may ask why? This is a long discussion, but basically React is designed with functional programming concepts in mind. One reason for this is that if we update the state directly, React will not be able to figure out what is changed, so it won’t know what part of the DOM to update. Another reason we don’t update the state directly is for performance reasons. Again, this is a topic for another post. For now, just take this from me: to update the state, we call the setState method of our components. You saw that our Counter component extends the Component class in React. By extending a class, we inherit all the functionality defined in that class. One of the methods defined in the Component class in React is the setState method.

So, modify the render method as follows:

render() {
    return (
            <button onClick={() => { this.setState({ value: this.state.value + 1 }) }}>Increment</button>

Here, we call the setState and pass an object. The properties in this object will overwrite the properties in our state property or merge with them. With this, we can increment state.value.

Note: Whenever we write a component, all of our code must be encapsulated inside of a parent element, such as a

. This is because when our code is compiled, each component must return only one parent component. So in our example, if we do not do this, the button tag would be unreachable.Now, save the changes. Go back to the browser and click the Increment button. Note that the value of the counter is now increasing by one with each click.

How React Works

You saw that our Counter component has a state. This is the data that we want to render in the DOM. We attached a handler to the click event of a button. When we click this button, we call the setState method. This will, in turn, update the state of our component. React will be notified. It figures out what element in the virtual DOM is updated. Then, it’ll update the real DOM to match the virtual DOM. We never had to get a reference to a DOM element (in this case the div) and set its innerText property.

Did you enjoy this post? If yes, please share it on social media. Feel free to drop your comments below.

Want to learn more?

This was a short and sweet introduction to React. There is more to React when it comes to building real-world applications. That’s why I’ve created a comprehensive React course. In this course, you’ll learn everything about React and build a real video rental application throughout the course. So, you’ll see all the moving parts coming together. More specifically you’ll learn all about:

Become a JavaScript developer - Learn (React, Node,Angular)

The Complete React Web Developer Course (2nd Edition)

Node with React: Fullstack Web Development

Beginner Full Stack Web Development: HTML, CSS, React & Node

React JS and Redux - Mastering Web Apps

React 16 - The Complete Guide (incl. React Router 4 & Redux)

MERN Stack Front To Back: Full Stack React, Redux & Node.js

*Originally published at *https://programmingwithmosh.com

How to perform CRUD operations and consume RESTful API using React?

How to perform CRUD operations and consume RESTful API using React?

In this post, we go through a tutorial on how to create a React application that can perform CRUD functions and take in data from a RESTful API. Recently we have experienced rapid growth of mobile, Internet-based communication. We have...

In this post, we go through a tutorial on how to create a React application that can perform CRUD functions and take in data from a RESTful API.

Recently we have experienced rapid growth of mobile, Internet-based communication. We have smartphones, tablets, netbooks, and other connected devices that create a need to serve appropriate content for each specific front-end profile. Also, the Internet is becoming available for new regions and social groups, constantly increasing web traffic. On the other side, users' computers and browsers, and JavaScript itself are getting more and more powerful, providing more possibilities for processing data on the web via the client-side. In this situation, the best solution can often be to send data as the response, instead of sending page content. That is, we don't need to reload the whole page on each request, but send back the corresponding data and let the client (front-end stuff) process the data.

We can develop a backend application exposing a remote API (usually based on the REST protocol) and a front-end (usually JavaScript) application, which communicates with the API and renders all the data on the device.

If backend data is consumed by humans, we need to develop a user interface (UI) to provide the possibility for users to manage the data. Modern web applications should have responsive and friendly UIs, ensuring adequate user experience. Also, modern UIs can be arbitrarily complex, with multi-panel, nested layouts, paging, progress bars, etc. In this case, the component model can be the right solution. React.js is a light-weight JavaScript framework, which is oriented toward the creation of component-based web UIs. React doesn't provide any means for communicating with the backend, but we can use any communication library from inside React components.

Before starting development, we need to set up a React.js development environment.

1. React.js Development Environment Set Up

There are several ways to use React.js. The simplest way is just to include React libraries in the

Learn React.js - Full Course for Beginners

Learn React.js - Full Course for Beginners

Learn the complete React-Redux front end system: React.js, Redux, React Router, React Hooks and Auth0

Other courses have made partial updates to older techniques and code, but this course is built from the ground up to include the most latest code and techniques from 2019+. You are getting the complete integrated modern techniques and code for React and Redux that are used in development today.

What you'll learn:

  • The Most Modern Version of React and Redux
  • Modern Authentication and Routing Patterns
  • The Knowledge and Skills to Apply to Front End Jobs
  • How React Works Under the Hood
  • The Knowledge to know how different Front End Technologies work together (enough knowledge to impress other engineers)
  • Modern ES5, ES6, ES7 Javascript Syntax.

Build a React Responsive Navigation Menu with React Hooks and Sass

Build a React Responsive Navigation Menu with React Hooks and Sass

In this video tutorial, we will learn how to build a responsive navbar with React, Reach Router, and Sass.

What Is Responsive Web Design?

Responsive Web design is the approach that suggests that design and development should respond to the user’s behavior and environment based on screen size, platform and orientation.

The practice consists of a mix of flexible grids and layouts, images and an intelligent use of CSS media queries. As the user switches from their laptop to iPad, the website should automatically switch to accommodate for resolution, image size and scripting abilities. One may also have to consider the settings on their devices; if they have a VPN for iOS on their iPad, for example, the website should not block the user’s access to the page. In other words, the website should have the technology to automatically respond to the user’s preferences. This would eliminate the need for a different design and development phase for each new gadget on the market.

Download and Run

git clone https://github.com/syntacticsolutions/react-navigation-menu.git
cd react-navigation-menu

In the project directory, you can run:

npm start

Build a React Responsive Navigation Menu with React Hooks and Sass

Runs the app in the development mode.

Open http://localhost:3000 to view it in the browser.
The page will reload if you make edits.

You will also see any lint errors in the console.

npm test

Launches the test runner in the interactive watch mode.

See the section about running tests for more information.

npm run build

Builds the app for production to the build folder.

It correctly bundles React in production mode and optimizes the build for the best performance.
The build is minified and the filenames include the hashes.

Your app is ready to be deployed!

See the section about deployment for more information.

npm run eject

Note: this is a one-way operation. Once you eject, you can’t go back!

If you aren’t satisfied with the build tool and configuration choices, you can eject at any time. This command will remove the single build dependency from your project.

Instead, it will copy all the configuration files and the transitive dependencies (Webpack, Babel, ESLint, etc) right into your project so you have full control over them. All of the commands except eject will still work, but they will point to the copied scripts so you can tweak them. At this point you’re on your own.

You don’t have to ever use eject. The curated feature set is suitable for small and middle deployments, and you shouldn’t feel obligated to use this feature. However we understand that this tool wouldn’t be useful if you couldn’t customize it when you are ready for it.

Learn More

You can learn more in the Create React App documentation.

To learn React, check out the React documentation.

Code Splitting

This section has moved here: https://facebook.github.io/create-react-app/docs/code-splitting

Analyzing the Bundle Size

This section has moved here: https://facebook.github.io/create-react-app/docs/analyzing-the-bundle-size

Making a Progressive Web App

This section has moved here: https://facebook.github.io/create-react-app/docs/making-a-progressive-web-app

Advanced Configuration

This section has moved here: https://facebook.github.io/create-react-app/docs/advanced-configuration


This section has moved here: https://facebook.github.io/create-react-app/docs/deployment

npm run build fails to minify

This section has moved here: https://facebook.github.io/create-react-app/docs/troubleshooting#npm-run-build-fails-to-minify

React-Redux with TypeScript

React-Redux with TypeScript

TypeScript is a typed superset of JavaScript. It has become popular recently in applications due to the benefits it can bring. If you are new to TypeScript it is highly recommended to become familiar with it first before proceeding.

TypeScript is a typed superset of JavaScript. It has become popular recently in applications due to the benefits it can bring. If you are new to TypeScript it is highly recommended to become familiar with it first before proceeding.

TypeScript is a great language to choose if you are a JavaScript developer and interested in moving towards a statically typed language. Using TypeScript is such a logical move for developers that are comfortable with JavaScript but haven’t written in languages that are statically typed (like C, JVM’s, Go, etc).

As I began my journey to TypeScript, (I’m most comfortable with JS, but have written a little bit in Go and C), I found it to be pretty easy to pick up. My initial thought was: “It really isn’t that bad typing all the argument in my function and typing the return value; what’s the fuss all about?” It was nice and simple until we had a project where we needed to create a React/Redux app in TypeScript.

It’s super easy to find material for React + JS, but as you begin to search for React + TS and especially React + Redux + TS, the amount of online tutorials (including YouTube videos) begin to dwindle significantly. I found myself scouring Medium, Stack Overflow, etc. for anything I could find to help explain how to set up the project, how types are flowing between files (especially once Redux is involved), and how to build with Webpack. This article is a way for me to solidify my knowledge of React + Redux + TS, and to hopefully provide some guidance for anyone else who is interested in using this tech stack for the front end. TypeScript is becoming more popular, so I hope this is useful to others in the community.

Prerequisites: I assume you’re aware of how React, Redux, and Webpack work, and also most concepts in TypeScript (at least interfaces and generics).

What are we gonna build? Just to keep it simple, we’ll build the infamous to-do list application. Remember that the purpose is to understand how to set up the project and know how TypeScript integrates with React and Redux. The features that this application will support are:

  1. Add a new item to a list.
  2. Remove an item from the list.

The code for the project can be found here: https://github.com/sterlingdeng/react-redux-ts-boilerplate.

For my project, I didn’t use create-react-app --typescript to get the project started. I found that it was a valuable learning experience to get it started from scratch. I’ll go step by step through the import files and folders needed to get this project up and running. Before we start, let me show you what the final structure looks like.

├── build
├── node_modules
├── public
│   ├── bundle.js
│   └── index.html
├── src
│   ├── App.tsx
│   ├── index.tsx
│   ├── actions
│   │   ├── actions.ts
│   │   └── index.ts
│   ├── components
│   │   ├── index.ts
│   │   └── TodoItem.tsx
│   ├── containers
│   │   └── TodoContainer.tsx
│   ├── reducers
│   │   ├── index.ts
│   │   └── todoReducers.ts
│   ├── store
│   │   └── store.ts
│   └── types
│       └── types.d.ts
├── .gitignore
├── package-lock.json
├── package.json
├── tslint.json
├── tsconfig.json
├── webpack.config.js
└── README.md

First, let’s look at the package.json file and install these dependencies using npm i.

"dependencies": {
    "@types/node": "^12.0.0",
    "@types/react": "^16.8.15",
    "@types/react-dom": "^16.8.4",
    "@types/react-redux": "^7.0.8",
    "react": "^16.8.6",
    "react-dom": "^16.8.6",
    "react-redux": "^7.0.3",
    "redux": "^4.0.1",
    "ts-loader": "^5.4.5",
    "typesafe-actions": "^4.2.0",
    "typescript": "^3.4.5",
    "webpack": "^4.30.0",
    "webpack-cli": "^3.3.1"

Let’s first look at the dependencies with the format @types/[npm module here]. If you aren’t familiar with what these modules are, look up https://github.com/DefinitelyTyped/DefinitelyTyped. Since most modules are written in JavaScript, they aren’t written with proper type definitions. Once you attempt to import a module without any type information into a project that is all typed, TypeScript will complain. To prevent this, the community of contributors at DefinitelyTyped create high-quality type definition of the most commonly used JavaScript modules so that those modules will integrate as seamlessly as possible with TS.

You are probably familiar with the next four. ts-loader is needed because Webpack needs a plugin to parse .ts and .tsx files. (This is similar to babel.)

typesafe-actions is a library I use with Redux + TypeScript. Without it, the files can get quite noisy in terms of declaring types for the Store, Reducer, and Actions. This library provides methods that infer type definition for redux code so that the files are a bit cleaner and focused.

webpack and webpack-cli are used to bundle the .ts and .tsx files into one.js file that can be sent to the front end.

Next, let’s look at thetsconfig.json file. The purpose of this file is to configure how you want the ts compiler to run.

  "compilerOptions": {
    "baseUrl": ".",
    "outDir": "build/dist",
    "module": "commonjs",
    "target": "es5",
    "sourceMap": true,
    "allowJs": true,
    "jsx": "react"

baseUrl denotes the folder. outDir directs the compiler where it should put the compiled code. module tells the compiler which JavaScript module types to use. target tells the compiler which JS version to target. sourceMap tells the compiler to create a bundle.js.map along with bundle.js. Because bundling will turn multiple files into one large .js file, troubleshooting code will be difficult because you wouldn’t easily know which file and at which line the code failed (since everything is just one big file). The .map file will map the bundled file to the respective unbundled file.

tslint.json provides options on how strict or loose you want the ts linter to be. The various options you can set for the linter can be found online.

Action Creators

Normally when I start projects with Redux, I begin at the action creators. Let’s quickly review the features that we need to implement: Adding an item to a list and removing an item from the list. This means we’ll need two action creators, one for adding and another for removing.

import { action } from "typesafe-actions";

// use typescript enum rather than action constants
export enum actionTypes {
  ADD = "ADD",

export const todoActions = {
  add: (item: string) => action(actionTypes.ADD, item),
  delete: (idx: number) => action(actionTypes.DELETE, idx)

In the actions.ts file, I’m using the enum feature in TS to create the action constants. Secondly, I’m using the action method provided from the typesafe-actions module. The first argument you pass into the method is a string which represents that action, and the second argument is the payload. The add method will add an item to the list of to-dos, and the deletemethod will remove an item, based on the provided index, from the list of to-dos.

In terms of type safety, what we want in our reducers file is the proper type of the payload, given a specific action. The feature in TypeScript that provides this support is called discriminated union and type guarding. Consider the example below:

// this is an example of discriminated unions
// this file isn't used in the project

interface ActionAdd {
  type: "ADD",
  payload: string

interface ActionDelete {
  type: "DELETE",
  payload: number

type Actions = ActionAdd | ActionDelete

function reducer(a: Actions) {
  switch(a.type) {
    case "ADD" : {
      // payload is a string
    case "DELETE" : {
      // payload is a number

Given the shape of the two action objects, we can discriminate between them based on the type property. Using control flow analysis, like if-else or switch-case statements, it’s very logical that in line 16, the only type that the payload can be is a string. Since we only have two actions, the remaining payload in line 22 will be a number. If you are interested in learning more about discriminated unions and type guarding, I would recommend learning more about it here and here.


After defining our action creators, let’s create the reducer for this project.

import * as MyTypes from "MyTypes";
import { actionTypes } from "../actions/";

interface ITodoModel {
  count: number;
  list: string[];

export const initialState: ITodoModel = {
  count: 2,
  list: ["Do the laundry", "Do the dishes"]

export const todoReducer = (state: ITodoModel = initialState, action: MyTypes.RootAction) => {
  switch (action.type) {
    case actionTypes.ADD: {
      return {
        count: state.count + 1,
        list: [...state.list, action.payload]
    case actionTypes.DELETE: {
      const oldList = [...state.list];
      oldList.splice(action.payload, 1);
      const newList = oldList;

      return {
        count: state.count - 1,
        list: newList
      return state;

In lines four through seven, I’m defining the model (or schema) of our Todostore. It will keep track of how many to-do items we have, as well as the array of strings. Lines nine through 12 are the initial state when the application first starts. Within the todoReducer function, we want type safety within the casestatements. Based on the earlier gist, we accomplished that by discriminated unions and type guarding, done by typing the action parameter. We have to first define an interface for every action object, and then create a union of them all and assign that to a type. This can get tedious if we have a lot of action creators — luckily, typesafe-actions has methods to help create the proper typing of the action creators without having to actually write out all the interfaces.

declare module "MyTypes" {
  import { StateType, ActionType } from "typesafe-actions";
  // 1 for reducer, 1 for action creators
  export type ReducerState = StateType<typeof import("../reducers").default>;
  export type RootAction = ActionType<typeof import("../actions/actions")>;

Ignoring line four for now and focusing on line five, we use a method called ActionType from the module, and import the actions from actions.ts to create the discriminated union types, which are then assigned to a type called RootAction. In line one of the todoReducers.ts, we import MyTypes and in line 14, we type the action parameter with MyTypes.RootAction. This allows us to have IntelliSense and autocompletion within the reducers!

Now that we have the reducer set up, the ReducerState type from the types.d.ts file allows TypeScript to infer the shape of the state object in the reducer function. This will provide IntelliSense when we try to access the payload object within the Reducer. An example of what that looks like is in the picture below.

IntelliSense in the Reducer

Redux Store

Finally, let’s hook up the reducer to the redux store.

import { createStore } from "redux";
import rootReducer from "../reducers";

const store = createStore(rootReducer);

export default store;

Let’s recap what we have accomplished up until this point. We have created and typed our action creators using the action method from typesafe-actions. We have created our types.d.ts file which provide type information on our action creators and reducer state. The reducer has been created and the actions are typed by using MyTypes.RootAction, which provide invaluable auto-completion information of the payload within the reducer’s case statements. And lastly, we created our Redux store.

React and TS

Let’s change gears and begin working on creating and typing our React components. I’ll go over examples of how to properly type both function and class based components, along with instructions on how to type both the props and state (for stateful components).


import * as React from "react";
import TodoContainer from "./containers/TodoContainer";

export const App: React.FC<{}> = () => {
  return (
      <h1>React Redux Typescript</h1>
      <TodoContainer />

App is a functional component that is typed by writing const App: React.FC<{}>. (FC refers to functional component.) If you aren’t familiar with generics (which is the <{}> ), I think of them like variables but for types. Since the shape of props and state can differ based on different use cases, generics are a way for us to, well, make the component generic! In this case, App doesn’t take any props; therefore, we pass in an empty object as the generic. How do we know that the generic is specifically for props? If you use VS code, IntelliSense will let you know what type it needs.

Where it says <P = {}> , it means type {} has been assigned to P, where Pstands for props. For class-based components, React will use S to refer to state. App is a functional component that receives no props and is not connected to the Redux store. Let’s go for something a little more complicated.


import * as React from "react";
import { connect } from "react-redux";
import { Dispatch } from "redux";
import * as MyTypes from "MyTypes";
import { actionTypes } from "../actions";
import { TodoItem } from "../components";

interface TodoContainerState {
  todoInput: string;

interface TodoContainerProps {
  count: number;
  todoList: string[];
  addToDo: (item: string) => object;
  deleteToDo: (idx: number) => object;

class TodoContainer extends React.Component<TodoContainerProps, TodoContainerState> {
  constructor(props) {
    this.state = {
      todoInput: ""

  handleTextChange = e => {
      todoInput: e.target.value

  handleButtonClick = () => {
      todoInput: ""

  handleDeleteButtonClick = (idx: number) => {
    console.log("deleting", idx);

  render() {
    let todoJSX: JSX.Element[] | JSX.Element;
    if (!this.props.todoList.length) {
      todoJSX = <p>No to do</p>;
    } else {
      todoJSX = this.props.todoList.map((item, idx) => {
        return (
          <TodoItem item={item} key={idx} idx={idx} handleDelete={this.handleDeleteButtonClick} />

    return (
          placeholder={"New To Do Here"}
        <button onClick={this.handleButtonClick}>Add To Do</button>

const MapStateToProps = (store: MyTypes.ReducerState) => {
  return {
    count: store.todo.count,
    todoList: store.todo.list

const MapDispatchToProps = (dispatch: Dispatch<MyTypes.RootAction>) => ({
  addToDo: (item: string) => dispatch({ type: actionTypes.ADD, payload: item }),
  deleteToDo: (idx: number) => dispatch({ type: actionTypes.DELETE, payload: idx })

export default connect(

OK, TodoContainer.tsx is the most complicated of them all, but I’ll walk you through what’s going on in the code. TodoContainer is a React Class Component because I need it to hold in its state the value for the input box. It is also connected to the redux store, so it’ll have MapStateToProps and MapDispatchToProps . First, I’ve definedTodoContainerState . Since I’ll be holding the value of the input box in state, I’ll type the property as a string.

Next, I’ve defined TodoContainerProps, which will be the shape of the Container’s props.

Because class-based components can have both state and props, we should expect that there should be at least two generics that we need to pass into React.Component.

P for Props and S for State

If you mouse over React.Component, you can see that it takes in three generics, P, S, and SS. The first two generics are props and state. I’m not quite sure whatSS is and what the use case is. If anyone knows, please let me know in the comments below.

After passing in the generics into React.Component , IntelliSense and autocompletion will work within this.state and for props.

Next, we want to type MapStateToProps and MapDispatchToProps. This is easily achievable by leveraging the MyTypes module that we built in the redux section. For MapStateToProps, we assign the store type to be MyTypes.ReducerState. An example of the IntelliSense it will provide is in the below screenshot.

IntelliSense for MapStateToProps

Lastly, we want to have type safety within MapDispatchToProps. The benefit that is provided is a type-safe payload given an action type.

Type-safe payloads

In the screenshot above, I purposely typed item as a boolean. Immediately, the TSServer will pick up that the boolean payload within MapDispatchToProps is not correct because it’s expecting the payload to be a string, given that the type is actionTypes.ADD. TodoContainer.tsx has the most going on since it is a class based React component, with both state and props, and is also connected to the store.

Before we wrap up, let’s look at our last component: TodoItem.tsx


This component is a functional component with props — code below.

import * as React from "react";

interface TodoItemProps {
  item: string;
  idx: number;
  handleDelete: (idx: number) => void;

export const TodoItem: React.FC<TodoItemProps> = props => {
  return (
      <button onClick={() => props.handleDelete(props.idx)}>X</button>

The shape of the props are defined in the interface TodoItemProps. The type information is passed into as a generic in React.FC. Doing so will provide auto-completion for props within the component. Awesome.

Another great feature that TypeScript provides when used with React is IntelliSense for props when rendering React Components within JSX. As an example, if you delete idx:number from TodoItemProps and then you navigate to TodoContainer.tsx, an error will appear at the place where you render <TodoItem />.

Property ‘idx’ does not exist

Because we removed idx from the TodoItemProps interface, TypeScript is letting us know that we have provided an additional prop that it couldn’t find, idx, into the component.

Lastly, let’s build the project using Webpack. In the command line, type npm run build. In the public folder within the root directory, you should see bundle.js alongsideindex.html. Open index.html in any browser and you should see a very simple, unstyled, to-do app.

After webpack build

I hope that I was able to demonstrate the power of TypeScript coupled with React and Redux. It may seem a bit overkill for our simple to-do list app — you just need to imagine the benefit of TS + React + Redux at scale. It will help new developers read the code quicker, provide more confidence in refactoring, and ultimately improve development speed.

If you need more reference and material, I used the following two Git repos to teach myself

Both these repos have proved invaluable for my learning, and I hope they will be the same for you.

How to build a Chat App with React Native

How to build a Chat App with React Native

In this tutorial, we’ll be looking at how to build a demo chat app in React Native

The following features:

  • Public and private chat rooms
  • Roles and permissions
  • Typing indicators
  • Read receipt
  • File uploads
  • Show online and offline users

Knowledge of **React **and React Native is required to follow this tutorial.

The following package versions are used. If you encounter any issues in compiling the app, try to use the following:

  • Node 11.2
  • Yarn 1.13
  • React Native 0.59

You’ll also need a Chatkit app instance. I assume you already know how to set it up. If not, then check out the official docs.

Lastly, you’ll need an ngrok account for exposing the server to the internet.

Chat App overview

As mentioned earlier, we will be building a chat app. The first screen that the user will see when they open the app is the Login screen. This is where they enter their username so they can log in. We will be creating the users in the **Chatkit **console later:

Once logged in, the app will show the list of rooms they can enter:

Once they’ve selected a room to enter, they’ll be greeted by the Chat app screen:

From the Chat screen, when a user clicks on the avatar of another member of a room, they can see the last message they have seen:

The list of members can be viewed when they click on the Users button in the header. The circle right beside the username indicates their online status:

Aside from those, the app will also have a file attachment and typing indicator feature. Image, audio, and video files can also be previewed.

You can find the code in this GitHub repo.

Setting up roles and permissions

Before we proceed, we first have to set up the roles and permissions for each user in the Chatkit console. We will set up seven users:

Three rooms will also be needed:

  • company
  • web_dev
  • mobile_dev

Everyone will be able to have chat in the company room. While the web and mobile users can only chat within their respective rooms. This can be implemented by means of roles and permissions:

For this app, we only have two roles. These will only be scoped in a specific room:

  • room-admin - check all the permissions.
  • room-member - check all the permissions except room:delete, room:update, room:join, room:leave, room:members:add, room:members:remove.

The only difference between the two is that the room-admin can add or remove users from the room. Though we won’t really be implementing it in the app.

Once you’ve created the roles, the next step is to assign the roles to each of the users. Web Admin and Mobile Admin will have the role of room-admin, while the rest of the users will have the role of room-member. Be sure to apply them to the room where they’re supposed to go:

Don’t forget to assign all of the users as a member of the company room. This time, the room admins will have the same role as the members.

Bootstrapping the app

For us to get into the crucial parts of the app quickly, I prepared a GitHub repo which contains some of the boilerplate code (custom components, navigation setup, styling). Clone it and switch to the starter branch:

    git clone https://github.com/anchetaWern/RNChatkitDemo
    git checkout starter

Whenever I mention “starter branch“, it means that I’m referring to existing code.
Next, install all the dependencies and link the relevant packages:

    react-native eject
    react-native link react-native-gesture-handler
    react-native link react-native-permissions
    react-native link react-native-document-picker
    react-native link react-native-fs
    react-native link react-native-config
    react-native link react-native-vector-icons
    react-native link rn-fetch-blob

One of the dependencies (React Native Audio Toolkit) doesn’t play nice with automatic linking. Be sure to check out their docs for information on how to set it up.

Next, we need to update the Android manifest file to allow the app to read from the external storage. This allows us to pick files from the device’s external storage:

    // android/app/src/main/AndroidManifest.xml
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
      <uses-permission android:name="android.permission.INTERNET" />
      <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

Lastly, update the android/app/build.gradle file and include the gradle file for React Native Config:

    apply from: "../../node_modules/react-native/react.gradle"
    apply from: project(':react-native-config').projectDir.getPath() + "/dotenv.gradle" // add this

Adding the server code

Now we’re ready to start coding. Let’s kick things off with the server. Some of the code for initializing Chatkit and running the server itself has already been added to the starter branch. All we have to do now is install the dependencies, update the .env file, and add the routes that the app will be consuming.

Start by install the dependencies:

    cd server

Next, update the .env file with the Chatkit credentials:


Now we can proceed with the code. The /users route allows us to fill the users array with users data that will be used when someone logs in. Later on, be sure to access <a href="http://localhost:5000/users" target="_blank">http://localhost:5000/users</a> on your browser before you try logging in a user. This is because the login code uses the data in the users array to get specific user data:

    // server/index.js
    let users = [];
    app.get("/users", async (req, res) => {
      try {
        users = await chatkit.getUsers();
        res.send({ users });
      } catch (get_users_err) {
        console.log("error getting users: ", get_users_err);

Note: We only have the above route to simplify things. You don’t really want to be exposing user data in a production app.
When a user logs in, the app makes a request to the /user route. This will return the user’s info based on their username:

    app.post("/user", async (req, res) => {
      const { username } = req.body;
      try {
        const user = users.find((usr) => usr.name == username);
        res.send({ user });
      } catch (get_user_err) {
        console.log("error getting user: ", get_user_err);

Next, add the route which returns the rooms that the user (the one supplied in the request body) is a member of. This is the reason why we went through the trouble of assigning each of the users to their rooms:

    app.post("/rooms", async (req, res) => {
      const { user_id } = req.body;
      try {
        const rooms = await chatkit.getUserRooms({
          userId: user_id
        res.send({ rooms });
      } catch (get_rooms_err) {
        console.log("error getting rooms: ", get_rooms_err);

The getUserRooms is preferable to the getJoinable rooms method because the rooms we created (except for the company room) are private. This means they won’t show up when you call getJoinableRooms. Another reason is that the room wouldn’t even be returned if the user is already a member of that room.
Lastly, add the route for returning the user permissions. This will be called when a user enters a specific room so that the app knows what the user can or cannot do in that specific room:

    app.post("/user/permissions", async(req, res) => {
      const { room_id, user_id } = req.body;
      try {
        const roles = await chatkit.getUserRoles({ userId: user_id });
        const role = roles.find(role => role.room_id == room_id);
        const permissions = (role) ? role.permissions : [];
        res.send({ permissions });
      } catch (user_permissions_err) {
        console.log("error getting user permissions: ", user_permissions_err);

The response data in the API call above is an array containing the individual permissions. Here’s an example: ['room:join', 'room:leave'].

Group screen

The Group screen is where the user will be redirected to when they have logged in to the app. We won’t go through the login code as it has already been pre-coded. All you need to know is that the Login screen sends a request to the /user route of the server. As you’ve seen earlier, this returns the user data. From this data, the only thing we want to pass to the Group screen is the user_id:

    // src/screens/Group.js
    state = {
      rooms: []

    constructor(props) {
      const { navigation } = this.props;
      this.user_id = navigation.getParam("id");

When the component is mounted, we send a request to the /rooms route. This returns the list of rooms that the user is a member of:

    async componentDidMount() {
      try {
        const response = await axios.post(`${CHAT_SERVER}/rooms`, { user_id: this.user_id });
        const { rooms } = response.data;
      } catch (get_rooms_err) {
        console.log("error getting rooms: ", get_rooms_err);

Next, render the list of rooms:

    render() {
      const { rooms } = this.state;
      return (
        <View style={styles.container}>
            rooms &&
              keyExtractor={(item) => item.id.toString()}

Here’s the code for rendering each list item. It has a button which when clicked by the user redirects them to the room they selected:

    renderRoom = ({ item }) => {
      return (
        <View style={styles.list_item}>
          <Text style={styles.list_item_text}>{item.name}</Text>
          <Button title="Enter" color="#0064e1" onPress={() => {
          }} />

Here’s the code for entering a chat room. This sends a request to the /user/permissions route which then returns the permissions for that specific room. From there, we determine if the user is a room admin if they have the room:members:add permission. This means that they can add new users to the room:

    enterChat = async (room) => {
      try {
        const response = await axios.post(`${CHAT_SERVER}/user/permissions`, { room_id: room.id, user_id: this.user_id });
        const { permissions } = response.data;
        const is_room_admin = (permissions.indexOf('room:members:add') !== -1);

        this.props.navigation.navigate("Chat", {
          user_id: this.user_id,
          room_id: room.id,
          room_name: room.name,

      } catch (get_permissions_err) {
        console.log("error getting permissions: ", get_permissions_err);

We won’t really be implementing the adding of users in this tutorial. This is just to show how permissions can be used to limit what the user can do within the app.##

Chat screen

We can now proceed to the main meat of the app. As we have lots of things to implement, I’ve divided it into multiple sections, each discussing a specific feature of the chat app.

Importing the dependencies

First, we import the dependencies:

    // src/screens/Chat.js
    import React, { Component } from "react";
    import { View, Text, ActivityIndicator, FlatList, TouchableOpacity, Alert } from "react-native";
    import { GiftedChat, Send, Message } from "react-native-gifted-chat"; // for the chat UI
    import { ChatManager, TokenProvider } from "@pusher/chatkit-client"; // for implementing chat functionality
    import axios from "axios"; // for making requests to the server
    import Config from "react-native-config"; // for reading .env file
    import Icon from "react-native-vector-icons/FontAwesome"; // for showing icons
    import { DocumentPicker, DocumentPickerUtil } from "react-native-document-picker"; // for picking files
    import * as mime from "react-native-mime-types"; // for determining the mime type of the picked file
    import Modal from "react-native-modal";
    import RNFetchBlob from "rn-fetch-blob"; // for converting the attached file to a blob
    import RNFS from "react-native-fs"; // for getting the base64 string representation of a file

Chatkit expects the file attachments to be a Blob. React Native doesn’t really have support for this format by default. So we use rn-fetch-blob as a polyfill to implement it. Later on, you’ll see this in action in the Attaching files section:

    const Blob = RNFetchBlob.polyfill.Blob;
    const fs = RNFetchBlob.fs;
    window.XMLHttpRequest = RNFetchBlob.polyfill.XMLHttpRequest;
    window.Blob = Blob;

Next, we have a few pre-coded components which are used to render either an audio or video player depending on the format of the attached file. Note that these components only support mp3 files for audio, and mp4 files for video:

    import ChatBubble from "../components/ChatBubble";
    import AudioPlayer from "../components/AudioPlayer";
    import VideoPlayer from "../components/VideoPlayer";

You can read my previous tutorial on playing audio and video file attachments in a Chatkit React Native app if you want to learn more about how those components are implemented
Lastly, update the .env file with your Chatkit config.

Initializing the chat code

In the Chat screen’s header, we add a button for opening the modal for viewing all the members of the room (whether they’re offline or online):

    class Chat extends Component {

      static navigationOptions = ({ navigation }) => {
        const { params } = navigation.state;
        return {
          headerTitle: params.room_name,
          headerRight: (
            <View style={styles.header_right}>
              <TouchableOpacity style={styles.header_button_container} onPress={params.showUsersModal}>
                <View style={styles.header_button}>
                  <Text style={styles.header_button_text}>Users</Text>

          headerStyle: {
            backgroundColor: "#333"
          headerTitleStyle: {
            color: "#FFF"

      // next: initialize state


Next, initialize the state:

    state = {
      company_users: null,
      room_users: null,
      messages: [],
      is_initialized: false, // if Chatkit is initialized or not
      is_picking_file: false, // to show/hide the loading animation when picking files
      // to show/hide the various modal windows:
      is_video_modal_visible: false,
      is_last_viewed_message_modal_visible: false,
      is_users_modal_visible: false, 
      is_typing: false, // if there's someone in the room who is currently typing
      typing_user: null, // the username of the user who is typing
      show_load_earlier: false, 
      viewed_user: null, // username of user whose read receipt is currently being viewed
      viewed_message: null // the text message being viewed

    // next: add constructor

Next, get the navigation params that were passed from the Group screen earlier:

    constructor(props) {
      const { navigation } = this.props;

      this.user_id = navigation.getParam("user_id");
      this.room_id = navigation.getParam("room_id");
      this.is_room_admin = navigation.getParam("is_room_admin");

      this.modal_types = {
        video: 'is_video_modal_visible',
        last_viewed_message: 'is_last_viewed_message_modal_visible',
        users: 'is_users_modal_visible'

    // next: add componentDidMount

Once the component is mounted, initialize Chatkit:

    async componentDidMount() {
        showUsersModal: this.showUsersModal

      try {
        const chatManager = new ChatManager({
          instanceLocator: CHATKIT_INSTANCE_LOCATOR_ID,
          userId: this.user_id,
          tokenProvider: new TokenProvider({ url: CHATKIT_TOKEN_PROVIDER_ENDPOINT })

        let currentUser = await chatManager.connect();
        this.currentUser = currentUser;

        // next: subscribe to room

      } catch (chat_mgr_err) {
        console.log("error with chat manager: ", chat_mgr_err);

We then subscribe to the room. We only need to subscribe to the hooks for receiving messages, and showing/hiding typing indicators:

    await this.currentUser.subscribeToRoomMultipart({
      roomId: this.room_id,
      hooks: {
        onMessage: this.onReceive,
        onUserStartedTyping: this.startTyping,
        onUserStoppedTyping: this.stopTyping

We don’t need to subscribe to the onPresenceChanged hook because the presence data from this.currentUser.users is live data. This means that when the users either offline or online, their presence state also changes, so the UI is automatically updated.
Lastly, we update the state with the room members data:

    await this.setState({
      is_initialized: true,
      room_users: this.currentUser.users

Chat UI

We can now proceed to the UI. Start by extracting the data that we need from the state:

    render() {
      const {
      } = this.state;

      // next: render the Chat UI

Next, render the chat UI. All the heavy lifting is already done for us by React Native Gifted Chat, so all we have to do is supply all the props that it needs:

    return (
      <View style={styles.container}>
        {(!is_initialized) && (

        {is_initialized && (
            onSend={messages => this.onSend(messages)} // function to execute when send button is clicked
              _id: this.user_id
            renderActions={this.renderCustomActions} // for rendering button for attaching files
            renderSend={this.renderSend} // custom send button UI
            renderMessage={this.renderMessage} // custom chat bubble UI
            onInputTextChanged={this.onTyping} // function to execute while the user is typing
            renderFooter={this.renderFooter} // for rendering the typing indicator
            extraData={{ typing_user }} // so that the footer will be re-rendered when the typing user is updated
            onPressAvatar={this.viewLastReadMessage} // function to execute when user avatar is clicked

            loadEarlier={show_load_earlier} // for loading earlier messages

        // next: add modals      


Next, render the modal for showing the fullscreen version of the attached video files:

    <Modal isVisible={is_video_modal_visible}>
      <View style={styles.modal}>
        <TouchableOpacity onPress={this.hideModal.bind(this, 'video')}>
          <Icon name={"close"} size={20} color={"#565656"} style={styles.close} />
        <VideoPlayer uri={video_uri} />

Next, render the modal for showing the last message viewed by a specific member of the room:

      viewed_user && viewed_message &&
      <Modal isVisible={is_last_viewed_message_modal_visible}>
        <View style={styles.modal}>
          <View style={styles.modal_header}>
            <Text style={styles.modal_header_text}>Last viewed msg: {viewed_user}</Text>
            <TouchableOpacity onPress={this.hideModal.bind(this, 'last_viewed_message')}>
              <Icon name={"close"} size={20} color={"#565656"} style={styles.close} />

          <View style={styles.modal_body}>
            <Text>Message: {viewed_message}</Text>

Next, render the modal for showing the list of members of the room:

      room_users &&
      <Modal isVisible={is_users_modal_visible}>
        <View style={styles.modal}>
          <View style={styles.modal_header}>
            <Text style={styles.modal_header_text}>Users</Text>
            <TouchableOpacity onPress={this.hideModal.bind(this, 'users')}>
              <Icon name={"close"} size={20} color={"#565656"} style={styles.close} />

          <View style={styles.modal_body}>
              keyExtractor={item => item.id.toString()}

Here’s the function for rendering each individual user. This will show a green circle next to the user’s name if they are online, and a gray circle if they’re offline:

    renderUser = ({ item }) => {
      const online_status = item.presenceStore[item.id];

      return (
        <View style={styles.list_item_body}>
          <View style={styles.list_item}>
            <View style={[styles.status_indicator, styles[online_status]]}></View>
            <Text style={styles.list_item_text}>{item.name}</Text>

Here’s the code for showing the users modal:

    showUsersModal = () => {
        is_users_modal_visible: true

Lastly, here’s the code for hiding a specific modal:

    hideModal = (type) => {
      const modal = this.modal_types[type];
        [modal]: false

Attaching files

The code for rendering the custom button for attaching files is already in the starter branch, so all we have to do is add the code for actually attaching a file. To implement this, we use the React Native Document Picker package. We call the DocumentPicker.show function to show the default file picker of the device’s operating system. We use the DocumentPickerUtil.allFiles function to specify that all file types can be selected by the user. You can also supply a specific file type if you want. From their source code, you can see that those methods simply return a mime-type wild card. Though we will only have previews for png, jpg, mp3, and mp4 files:

    openFilePicker = async () => {
      await this.setState({
        is_picking_file: true // show the loader instead of the button for picking files to prevent the user from clicking it again

        filetype: [DocumentPickerUtil.allFiles()],
      }, async (err, file) => {
        if (!err) { // if there's no error in picking the file

          // next: convert the file to a blob

          is_picking_file: false

Next, we determine the mime type of the file and convert it to its base64 string representation using the react-native-fs package. From there, we convert it to a Blob using the rn-fetch-blob package. As you learned earlier, this acts as a polyfill for implementing Blobs in the React Native environment. Lastly, we temporarily store the name, type, and the Blob representation of the file so that we can easily get it later when we send a message:

    try {
      const file_type = mime.contentType(file.fileName);
      const base64 = await RNFS.readFile(file.uri, "base64");

      const file_blob = await Blob.build(base64, { type: `${file_type};BASE64` });

      this.attachment = {
        file_blob: file_blob,
        file_name: file.fileName,
        file_type: file_type

      Alert.alert("Success", "File attached!");

    } catch (attach_err) {
      console.log("error attaching file: ", attach_err);

Sending messages

The code for sending messages is already included in the starter branch. But we need to update it so that it sends multi-part messages (text with attachment). Replace the existing onSend method with the following. The main difference here is that the text message is included in the message_parts array. This allows us to supply different kinds of content to an individual message. In this case, the other type is an attachment. If the user has selected an attachment, we push it into the message_parts array:

    onSend = async ([message]) => {
      let message_parts = [
        { type: "text/plain", content: message.text }

      if (this.attachment) {
        const { file_blob, file_name, file_type } = this.attachment;
          file: file_blob, // the file Blob
          name: file_name, // the file name
          type: file_type // the file type

        is_sending: true // show the loading animation for sending a message

      // next: send message

Next, we send the message. The main difference here is that we’re now using the sendMultipartMessage method instead of the sendSimpleMessage method. Another important thing to note is that when a user sends a message, we also assume that they’ve already read the last message they received. So we set a read cursor using the ID of the last message they received:

    try {
      if (this.last_message_id) {
        const set_cursor_response = await this.currentUser.setReadCursor({
          roomId: this.room_id,
          position: this.last_message_id // the ID of the last message they received
      // send the message
      await this.currentUser.sendMultipartMessage({
        roomId: this.room_id,
        parts: message_parts

      this.attachment = null;
      await this.setState({
        is_sending: false // hide the loading animation
    } catch (send_msg_err) {
      console.log("error sending message: ", send_msg_err);

Receiving messages

The code for receiving messages has already been included in the starter branch, but we need to update it so it sets the last_message_id that we used in the code for sending a message earlier:

    onReceive = async (data) => {
      this.last_message_id = data.id; // add this
      // ...

Next, replace the existing getMessage function with the following:

    getMessage = async ({ id, sender, parts, createdAt }) => {

      const text = parts.find(part => part.partType === 'inline').payload.content;
      const attachment = parts.find(part => part.partType === 'attachment');

      const attachment_url = (attachment) ? await attachment.payload.url() : null;
      const attachment_type = (attachment) ? attachment.payload.type : null;

      const msg_data = {
        _id: id,
        text: text,
        createdAt: new Date(createdAt),
        user: {
          _id: sender.id,
          name: sender.name,
          avatar: `https://ui-avatars.com/api/?background=d88413&color=FFF&name=${sender.name}`

      if (attachment) {
        Object.assign(msg_data, { attachment: { url: attachment_url, type: attachment_type } });

      if (attachment && attachment_type.indexOf('video') !== -1) {
        Object.assign(msg_data, { video: attachment_url });

      if (attachment && attachment_type.indexOf('image') !== -1) {
        Object.assign(msg_data, { image: attachment_url });

      return {
        message: msg_data

We’re using the UI Avatars API to automatically generate an image which matches the user’s initials.
In the code above, the most important distinction is the way we’re getting the text. In this case, the message is already considered a multipart message instead of a simple plain-text message. The first part you specify should always be the text. While the parts that follow can be a file attachment or a URL. The type of a specific part can either be inline, url, or attachment. In this case, we’re handling both inline and attachment types. If you specify, text/plain as the type for a message part, it’s automatically considered as inline. And if you specify a file to a message part, it’s automatically considered as an attachment.

To get to the actual text of an inline message part, we simply extract payload.content:

    const text = parts.find(part => part.partType === 'inline').payload.content;

But for an attachment message part, you have to call the payload’s url() method in order to get the direct URL to the file. This is what we use for previewing the files:

    const attachment = parts.find(part => part.partType === 'attachment');
    const attachment_url = (attachment) ? await attachment.payload.url() : null;

Next, add the renderMessage function. We don’t have this on the starter branch because we’re only rendering plain text previously. This time though, we need to cater for audio (mp3), and video (mp4) files as well. We only render a custom chat bubble if it’s an audio file because Gifted Chat already has a feature for rendering previews for image and video files. If it’s a video though, we supply the onLongPress prop to Gifted Chat’s <Message> component. This allows us to listen for the event when a chat bubble is long-pressed. It’s what we use to render the fullscreen video:

    renderMessage = (msg) => {
      const { attachment } = msg.currentMessage;
      const renderBubble = (attachment && attachment.type.indexOf('audio') !== -1) ? this.renderPreview.bind(this, attachment.url) : null;
      const onLongPress = (attachment  && attachment.type.indexOf('video') !== -1) ? this.onLongPressMessageBubble.bind(this, attachment.url) : null;

      const modified_msg = {
        videoProps: {
          paused: true // don't autoplay the video because it's just a preview
      return <Message {...modified_msg} />

When a chat bubble that has a custom onLongPress method is long pressed, the app opens the modal for viewing the fullscreen video:

    onLongPressMessageBubble = (link) => {
        is_video_modal_visible: true,
        video_uri: link // the direct link to the video

Next, here’s the code for rendering a custom chat bubble. This makes use of the <AudioPlayer> component which has already been pre-coded:

    renderPreview = (uri, bubbleProps) => {
      const text_color = (bubbleProps.position == 'right') ? '#FFF' : '#000';
      const modified_bubbleProps = {
      return (
        <ChatBubble {...modified_bubbleProps}>
          <AudioPlayer url={uri} />

Typing indicators

To implement the typing indicators, we use Chatkit’s isTypingIn method to set the room where the current user is currently typing in. This will trigger the onUserStartedTyping hook on the other members of the room who are currently online:

    onTyping = async () => {
      try {
        await this.currentUser.isTypingIn({ roomId: this.room_id });
      } catch (typing_err) {
        console.log("error setting is typing: ", typing_err);

When the onUserStartedTyping hook is triggered, the following function is executed. This shows the chat UI’s footer text which displays the typing indicator:

    startTyping = (user) => {
        is_typing: true,
        typing_user: user.name

If the user stops typing, the onUserStoppedTyping hook is automatically triggered so the following function is executed as well. This hides the chat UI’s footer text:

    stopTyping = (user) => {
        is_typing: false,
        typing_user: null

Here’s the code for rendering the custom footer. All it does is show the name of the user who is currently typing in the chat room:

    renderFooter = () => {
      const { is_typing, typing_user } = this.state;
      if (is_typing) {
        return (
          <View style={styles.footerContainer}>
            <Text style={styles.footerText}>
              {typing_user} is typing...
      return null;

Read receipt

The last feature that we’re going to implement is the read receipt. This allows the current user to view the last message that another member of the room has read (or get all of the user’s read cursors). This makes use of Chatkit’s readCursor method to fetch the ID of the latest message that a specific user has marked as read (via the setReadCursor method):

    viewLastReadMessage = async (data) => {
      try {
        const cursor = await this.currentUser.readCursor({
          userId: data.userId,
          roomId: this.room_id

        const viewed_message = this.state.messages.find(msg => msg._id == cursor.position);

        await this.setState({
          viewed_user: data.name,
          is_last_viewed_message_modal_visible: true,
          viewed_message: viewed_message.text
      } catch (view_last_msg_err) {
        console.log("error viewing last message: ", view_last_msg_err);

Users can only view the message if it has already been loaded in their chat screen. If the message doesn’t show up then it means that the member they selected hasn’t read any of the recent messages that the current user is able to view.## Running the Chat app

At this point, you can now run the app. Start by running the server and exposing it to the internet using ngrok:

    cd server
    yarn start
    ~/Downloads/ngrok http 5000

Update the login and chat screen with your ngrok URL:

    // src/screens/Login.js, src/screens/Group.js, src/screens/Chat.js

Next, delete the node_modules/react-native-gifted-chat/node_modules/react-native-video folder. This is because we also have React Native Video as a dependency for the app. It’s conflicting with Gifted Chat’s copy, so we need to delete it.

Finally, run the app:

    react-native run-android
    react-native run-ios

Before you log a user in, be sure to visit <a href="http://localhost:5000/users" target="_blank">http://localhost:5000/users</a> on your browser to populate the users array in the server.


In this tutorial, you learned how to use various **Chatkit **features within a React Native app. Specifically, you learned how to implement roles and permissions, read receipts, file uploads, and typing indicators.

You can find the code in this GitHub repo.