Build customer list management App with React and TypeScript

Build customer list management App with React and TypeScript

How to build a chat app with React, TypeScript .. We already mentioned the main technologies we will be using, but let's define a proper list

Introduction

TypeScript has brought a lot of improvement into how JavaScript developers structure and write code for apps, especially web applications. Defined as a superset of JavaScript, TypeScript behaves identically to JavaScript but with extra features designed to help developers build larger and more complex programs with fewer or no bugs. TypeScript is increasingly gaining popularity; adopted by major companies like Google for the Angular web framework. The Nest.js back-end framework was also built with TypeScript.

One of the ways to improve productivity as a developer is the ability to implement new features as quickly as possible without any concern over breaking the existing app in production. To achieve this, writing statically typed code is a style adopted by many seasoned developers. Statically typed programming languages like TypeScript enforce an association for every variable with a data type; such as a string, integer, boolean, and so on. One of the major benefits of using a statically typed programming language is that type checking is completed at compile time, therefore developers can see errors in their code at a very early stage.

React is an open-source JavaScript library, which developers use to create high-end user interfaces for scalable web applications. The great performance and dynamic user interfaces built with React for single-page applications make it a popular choice among developers.

In this tutorial, you will create a customer list management application with a separate REST API backend and a frontend built with React and TypeScript. You will build the backend using a fake REST API named json-server. You'll use it to quickly set up a CRUD (Create, Read, Update, and Delete) backend. Consequently you can focus on handling the front-end logic of an application using React and TypeScript.

Prerequisites

To complete this tutorial, you will need:

  • A local installation of Node.js (at least v6) and npm (at least v5.2). Node.js is a JavaScript run-time environment that allows you to run your code outside of the browser. It comes with a pre-installed package manager called npm, which lets you install and update packages. To install these on macOS or Ubuntu 18.04, follow the steps in How to Install Node.js and Create a Local Development Environment on macOS or the "Installing Using a PPA" section of How To Install Node.js on Ubuntu 18.04.
  • A local installation of Yarn; follow these steps to install Yarn on your operating system.
  • A basic understanding of TypeScript and JavaScript.
  • A text editor installed; such as Visual Studio Code, Atom, or Sublime Text.

Step 1 — Installing TypeScript and Creating the React Application

In this step, you will install the TypeScript package globally on your machine by using the Node Package Manager (npm). After that, you will also install React and its dependencies, and check that your React app is working by running the development server.

To begin, open a terminal and run the following command to install TypeScript:

npm install -g typescript

Once the installation process is complete, execute the following command to check your installation of TypeScript:

tsc -v

You will see the current version installed on your machine:

Output
Version 3.4.5

Next, you will install the React application by using the create-react-app tool to set up the application with a single command. You'll use the npx command, which is a package runner tool that comes with npm 5.2+. The create-react-app tool has built-in support for working with TypeScript without any extra configuration required. Run the following command to create and install a new React application named typescript-react-app:

npx create-react-app typescript-react-app --typescript

The preceding command will create a new React application with the name typescript-react-app. The --typescript flag will set the default filetype for React components to .tsx.

Before you complete this section, the application will require moving from one port to another. To do that, you will need to install a routing library for your React application named React Router and its corresponding TypeScript definitions. You will use yarn to install the library and other packages for this project. This is because yarn is faster, especially for installing dependencies for a React application. Move into the newly created project folder and then install React Router with the following command:

cd typescript-react-app
yarn add react-router-dom

You now have the React Router package, which will provide the routing functionality within your project. Next, run the following command to install the TypeScript definitions for React Router:

yarn add @types/react-router-dom

Now you'll install axios, which is a promised-based HTTP client for browsers, to help with the process of performing HTTP requests from the different components that you will create within the application:

yarn add axios

Once the installation process is complete, start the development server with:

yarn start
Your application will be running on http://localhost:3000.
Version 3.4.5

Next, you will install the React application by using the create-react-app tool to set up the application with a single command. You'll use the npx command, which is a package runner tool that comes with npm 5.2+. The create-react-app tool has built-in support for working with TypeScript without any extra configuration required. Run the following command to create and install a new React application named typescript-react-app:

You have successfully installed TypeScript, created a new React application, and installed React Router in order to help with navigating from one page of the application to another. In the next section, you will set up the back-end server for the application.

Step 2 — Creating a JSON Server

In this step, you'll create a mock server that your React application can quickly connect with, as well as use its resources. It is important to note that this back-end service is not suitable for an application in production. You can use Nest.js, Express, or any other back-end technology to build a RESTful API in production. json-server is a useful tool whenever you need to create a prototype and mock a back-end server.

You can use either npm or yarn to install json-server on your machine. This will make it available from any directory of your project whenever you might need to make use of it. Open a new terminal window and run this command to install json-server while you are still within the project directory:

yarn global add json-server

Next, you will create a JSON file that will contain the data that will be exposed by the REST API. For the objects specified in this file (which you'll create), a CRUD endpoint will be generated automatically. To begin, create a new folder named server and then move into it:

mkdir server
cd server

Now, use nano to create and open a new file named db.json:

nano db.json

Add the following content to the file:

/server/db.json
{
    "customers": [
        {
            "id": 1,
            "first_name": "Customer_1",
            "last_name": "Customer_11",
            "email": "[email protected]",
            "phone": "00000000000",
            "address": "Customer_1 Address",
            "description": "Customer_1 description"
        },
        {
            "id": 2,
            "first_name": "Customer_2",
            "last_name": "Customer_2",
            "email": "[email protected]",
            "phone": "00000000000",
            "address": "Customer_2 Adress",
            "description": "Customer_2 Description"
        }
    ]
}

The JSON structure consists of a customer object, which has two datasets assigned. Each customer consists of seven properties: iddescriptionfirst_namelast_nameemailphone, and address.

Save and exit the file.

By default, the json-server runs on port 3000—this is the same port on which your React application runs. To avoid conflict, you can change the default port for the json-server. To do that, move to the root directory of the application:

cd ~/typescript-react-app

Open the application with your preferred text editor and create a new file named json-server.json:

nano json-server.json

Now insert the following to update the port number:

/json-server.json


{
    "port": 5000
}

This will act as the configuration file for the json-server and it will ensure that the server runs on the port specified in it at all times.

Save and exit the file.

To run the server, use the following command:

json-server --watch server/db.json

This will start the json-server on port 5000. If you navigate to http://localhost:5000/customersin your browser, you will see the server showing your customer list.

To streamline the process of running the json-server, you can update package.json with a new property named server to the scripts object as shown here:

/package.json
{
...
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject",
    "server": "json-server --watch server/db.json"
  },
...
}

Save and exit the file.

Now anytime you wish to start the json-server, all you have to do is run yarn server from the terminal.

You've created a simple REST API that you will use as the back-end server for this application. You also created a customer JSON object that will be used as the default data for the REST API. Lastly, you configured an alternative port for the back-end server powered by json-server. Next, you will build reusable components for your application.

Step 3 — Creating Reusable Components

In this section, you will create the required React components for the application. This will include components to create, display, and edit the details of a particular customer in the database respectively. You'll also build some of the TypeScript interfaces for your application.

To begin, move back to the terminal where you have the React application running and stop the development server with CTRL + C. Next, navigate to the ./src/ folder:

cd ./src/

Then, create a new folder named components inside of it and move into the new folder:

mkdir components
cd components

Within the newly created folder, create a customer folder and then move into it:

mkdir customer
cd customer

Now create two new files named Create.tsx and Edit.tsx:

touch Create.tsx Edit.tsx

These files are React reusable components that will render the forms and hold all the business logic for creating and editing the details of a customer respectively.

Open the Create.tsx file in your text editor and add the following code:

/src/components/customer/Create.tsx
import * as React from 'react';
import axios from 'axios';
import { RouteComponentProps, withRouter } from 'react-router-dom';

export interface IValues {
first_name: string,
last_name: string,
email: string,
phone: string,
address: string,
description: string,
}
export interface IFormState {
[key: string]: any;
values: IValues[];
submitSuccess: boolean;
loading: boolean;
}

Here you've imported Reactaxios, and other required components necessary for routing from the React Router package. After that you created two new interfaces named IValues and IFormStateTypeScript interfaces help to define the specific type of values that should be passed to an object and enforce consistency throughout an application. This ensures that bugs are less likely to appear in your program.

Next, you will build a Create component that extends React.Component. Add the following code to the Create.tsx file immediately after the IFormState interface:

/src/components/customer/Create.tsx
...
class Create extends React.Component<RouteComponentProps, IFormState> {
constructor(props: RouteComponentProps) {
super(props);
this.state = {
first_name: '',
last_name: '',
email: '',
phone: '',
address: '',
description: '',
values: [],
loading: false,
submitSuccess: false,
}
}
}
export default withRouter(Create)

Here you've defined a React component in Typescript. In this case, the Create class component accepts props (short for “properties”) of type RouteComponentProps and uses a state of type IFormState. Then, inside the constructor, you initialized the state object and defined all the variables that will represent the rendered values for a customer.

Next, add these methods within the Create class component, just after the constructor. You'll use these methods to process customer forms and handle all changes in the input fields:

/src/components/customer/Create.tsx
...
values: [],
loading: false,
submitSuccess: false,
}
}

private processFormSubmission = (e: React.FormEvent<HTMLFormElement>): void => {
e.preventDefault();
this.setState({ loading: true });
const formData = {
first_name: this.state.first_name,
last_name: this.state.last_name,
email: this.state.email,
phone: this.state.phone,
address: this.state.address,
description: this.state.description,
}
this.setState({ submitSuccess: true, values: [...this.state.values, formData], loading: false });
axios.post(http://localhost:5000/customers, formData).then(data => [
setTimeout(() => {
this.props.history.push('/');
}, 1500)
]);
}

  private handleInputChanges = (e: React.FormEvent&lt;HTMLInputElement&gt;) =&gt; {
      e.preventDefault();
      this.setState({
          [e.currentTarget.name]: e.currentTarget.value,
  })

}

...
export default withRouter(Create)
...

The processFormSubmission() method receives the details of the customer from the application state and posts it to the database using axios. The handleInputChanges() uses React.FormEventto obtain the values of all input fields and calls this.setState() to update the state of the application.

Next, add the render() method within the Create class component immediately after the handleInputchanges() method. This render() method will display the form to create a new customer in the application:

/src/components/customer/Create.tsx
...
public render() {
const { submitSuccess, loading } = this.state;
return (
<div>
<div className={"col-md-12 form-wrapper"}>
<h2> Create Post </h2>
{!submitSuccess && (
<div className="alert alert-info" role="alert">
Fill the form below to create a new post
</div>
)}
{submitSuccess && (
<div className="alert alert-info" role="alert">
The form was successfully submitted!
</div>
)}
<form id={"create-post-form"} onSubmit={this.processFormSubmission} noValidate={true}>
<div className="form-group col-md-12">
<label htmlFor="first_name"> First Name </label>
<input type="text" id="first_name" onChange={(e) => this.handleInputChanges(e)} name="first_name" className="form-control" placeholder="Enter customer's first name" />
</div>
<div className="form-group col-md-12">
<label htmlFor="last_name"> Last Name </label>
<input type="text" id="last_name" onChange={(e) => this.handleInputChanges(e)} name="last_name" className="form-control" placeholder="Enter customer's last name" />
</div>
<div className="form-group col-md-12">
<label htmlFor="email"> Email </label>
<input type="email" id="email" onChange={(e) => this.handleInputChanges(e)} name="email" className="form-control" placeholder="Enter customer's email address" />
</div>
<div className="form-group col-md-12">
<label htmlFor="phone"> Phone </label>
<input type="text" id="phone" onChange={(e) => this.handleInputChanges(e)} name="phone" className="form-control" placeholder="Enter customer's phone number" />
</div>
<div className="form-group col-md-12">
<label htmlFor="address"> Address </label>
<input type="text" id="address" onChange={(e) => this.handleInputChanges(e)} name="address" className="form-control" placeholder="Enter customer's address" />
</div>
<div className="form-group col-md-12">
<label htmlFor="description"> Description </label>
<input type="text" id="description" onChange={(e) => this.handleInputChanges(e)} name="description" className="form-control" placeholder="Enter Description" />
</div>
<div className="form-group col-md-4 pull-right">
<button className="btn btn-success" type="submit">
Create Customer
</button>
{loading &&
<span className="fa fa-circle-o-notch fa-spin" />
}
</div>
</form>
</div>
</div>
)
}
...

Here, you created a form with the input fields to hold the values of the first_namelast_nameemailphoneaddress, and description of a customer. Each of the input fields have a method handleInputChanges() that runs on every keystroke, updating the React state with the value it obtains from the input field. Furthermore, depending on the state of the application, a boolean variable named submitSuccess will control the message that the application will display before and after creating a new customer.

You can see the complete code for this file in this GitHub repository.

Save and exit Create.tsx.

Now that you have added the appropriate logic to the Create component file for the application, you'll proceed to add contents for the Edit component file.

Open your Edit.tsx file within the customer folder, and start by adding the following content to import Reactaxios, and also define TypeScript interfaces:

/src/components/customer/Edit.tsx

import * as React from 'react';
import { RouteComponentProps, withRouter } from 'react-router-dom';
import axios from 'axios';

export interface IValues {
[key: string]: any;
}
export interface IFormState {
id: number,
customer: any;
values: IValues[];
submitSuccess: boolean;
loading: boolean;
}

Similarly to the Create component, you import the required modules and create IValues and IFormState interfaces respectively. The IValues interface defines the data type for the input fields' values, while you'll use IFormState to declare the expected type for the state object of the application.

Next, create the EditCustomer class component directly after the IFormState interface block as shown here:

/src/components/customer/Edit.tsx

...
class EditCustomer extends React.Component<RouteComponentProps<any>, IFormState> {
constructor(props: RouteComponentProps) {
super(props);
this.state = {
id: this.props.match.params.id,
customer: {},
values: [],
loading: false,
submitSuccess: false,
}
}
}
export default withRouter(EditCustomer)

This component takes the RouteComponentProps<any> and an interface of IFormState as a parameter. You use the addition of <any> to the RouteComponentProps because whenever React Router parses path parameters, it doesn’t do any type conversion to ascertain whether the type of the data is number or string. Since you're expecting a parameter for uniqueId of a customer, it is safer to use any.

Now add the following methods within the component:

/src/components/customer/Edit.tsx

    public componentDidMount(): void {
axios.get(http://localhost:5000/customers/${this.state.id}).then(data => {
this.setState({ customer: data.data });
})
}

private processFormSubmission = async (e: React.FormEvent&lt;HTMLFormElement&gt;): Promise&lt;void&gt; =&gt; {
    e.preventDefault();
    this.setState({ loading: true });
    axios.patch(`http://localhost:5000/customers/${this.state.id}`, this.state.values).then(data =&gt; {
        this.setState({ submitSuccess: true, loading: false })
        setTimeout(() =&gt; {
            this.props.history.push('/');
        }, 1500)
    })
}

private setValues = (values: IValues) =&gt; {
    this.setState({ values: { ...this.state.values, ...values } });
}
private handleInputChanges = (e: React.FormEvent&lt;HTMLInputElement&gt;) =&gt; {
    e.preventDefault();
    this.setValues({ [e.currentTarget.id]: e.currentTarget.value })
}

...
}

export default withRouter(EditCustomer)

First, you add a componentDidMount() method, which is a lifecycle method that is being called when the component is created. The method takes the id obtained from the route parameter to identify a particular customer as a parameter, uses it to retrieve their details from the database and then populates the form with it. Furthermore, you add methods to process form submission and handle changes made to the values of the input fields.

Lastly, add the render() method for the Edit component:

/src/components/customer/Edit.tsx

...
public render() {
const { submitSuccess, loading } = this.state;
return (
<div className="App">
{this.state.customer &&
<div>
< h1 > Customer List Management App</h1>
<p> Built with React.js and TypeScript </p>

                    &lt;div&gt;
                        &lt;div className={"col-md-12 form-wrapper"}&gt;
                            &lt;h2&gt; Edit Customer &lt;/h2&gt;
                            {submitSuccess &amp;&amp; (
                                &lt;div className="alert alert-info" role="alert"&gt;
                                    Customer's details has been edited successfully &lt;/div&gt;
                            )}
                            &lt;form id={"create-post-form"} onSubmit={this.processFormSubmission} noValidate={true}&gt;
                                &lt;div className="form-group col-md-12"&gt;
                                    &lt;label htmlFor="first_name"&gt; First Name &lt;/label&gt;
                                    &lt;input type="text" id="first_name" defaultValue={this.state.customer.first_name} onChange={(e) =&gt; this.handleInputChanges(e)} name="first_name" className="form-control" placeholder="Enter customer's first name" /&gt;
                                &lt;/div&gt;
                                &lt;div className="form-group col-md-12"&gt;
                                    &lt;label htmlFor="last_name"&gt; Last Name &lt;/label&gt;
                                    &lt;input type="text" id="last_name" defaultValue={this.state.customer.last_name} onChange={(e) =&gt; this.handleInputChanges(e)} name="last_name" className="form-control" placeholder="Enter customer's last name" /&gt;
                                &lt;/div&gt;
                                &lt;div className="form-group col-md-12"&gt;
                                    &lt;label htmlFor="email"&gt; Email &lt;/label&gt;
                                    &lt;input type="email" id="email" defaultValue={this.state.customer.email} onChange={(e) =&gt; this.handleInputChanges(e)} name="email" className="form-control" placeholder="Enter customer's email address" /&gt;
                                &lt;/div&gt;
                                &lt;div className="form-group col-md-12"&gt;
                                    &lt;label htmlFor="phone"&gt; Phone &lt;/label&gt;
                                    &lt;input type="text" id="phone" defaultValue={this.state.customer.phone} onChange={(e) =&gt; this.handleInputChanges(e)} name="phone" className="form-control" placeholder="Enter customer's phone number" /&gt;
                                &lt;/div&gt;
                                &lt;div className="form-group col-md-12"&gt;
                                    &lt;label htmlFor="address"&gt; Address &lt;/label&gt;
                                    &lt;input type="text" id="address" defaultValue={this.state.customer.address} onChange={(e) =&gt; this.handleInputChanges(e)} name="address" className="form-control" placeholder="Enter customer's address" /&gt;
                                &lt;/div&gt;
                                &lt;div className="form-group col-md-12"&gt;
                                    &lt;label htmlFor="description"&gt; Description &lt;/label&gt;
                                    &lt;input type="text" id="description" defaultValue={this.state.customer.description} onChange={(e) =&gt; this.handleInputChanges(e)} name="description" className="form-control" placeholder="Enter Description" /&gt;
                                &lt;/div&gt;
                                &lt;div className="form-group col-md-4 pull-right"&gt;
                                    &lt;button className="btn btn-success" type="submit"&gt;
                                        Edit Customer &lt;/button&gt;
                                    {loading &amp;&amp;
                                        &lt;span className="fa fa-circle-o-notch fa-spin" /&gt;
                                    }
                                &lt;/div&gt;
                            &lt;/form&gt;
                        &lt;/div&gt;
                    &lt;/div&gt;
                &lt;/div&gt;
            }
        &lt;/div&gt;
    )
}

...

Here, you created a form to edit the details of a particular customer, and then populated the input fields within that form with the customer's details that your application's state obtained. Similarly to the Create component, changes made to all the input fields will be handled by the handleInputChanges() method.

You can see the complete code for this file in this GitHub repository.

Save and exit Edit.tsx.

To view the complete list of customers created within the application, you’ll create a new component within the ./src/components folder and name it Home.tsx:

cd ./src/components
nano Home.tsx

Add the following content:

/src/components/Home.tsx

import * as React from 'react';
import { Link, RouteComponentProps } from 'react-router-dom';
import axios from 'axios';

interface IState {
customers: any[];
}

export default class Home extends React.Component<RouteComponentProps, IState> {
constructor(props: RouteComponentProps) {
super(props);
this.state = { customers: [] }
}
public componentDidMount(): void {
axios.get(http://localhost:5000/customers).then(data => {
this.setState({ customers: data.data })
})
}
public deleteCustomer(id: number) {
axios.delete(http://localhost:5000/customers/${id}).then(data => {
const index = this.state.customers.findIndex(customer => customer.id === id);
this.state.customers.splice(index, 1);
this.props.history.push('/');
})
}
}

Here, you've imported Reactaxios, and other required components from React Router. You created two new methods within the Home component:

  • componentDidMount(): The application invokes this method immediately after a component is mounted. Its responsibility here is to retrieve the list of customers and update the home page with it.
  • deleteCustomer(): This method will accept an id as a parameter and will delete the details of the customer identified with that id from the database.

Now add the render() method to display the table that holds the list of customers for the Homecomponent:

/src/components/Home.tsx

...
public render() {
const customers = this.state.customers;
return (
<div>
{customers.length === 0 && (
<div className="text-center">
<h2>No customer found at the moment</h2>
</div>
)}
<div className="container">
<div className="row">
<table className="table table-bordered">
<thead className="thead-light">
<tr>
<th scope="col">Firstname</th>
<th scope="col">Lastname</th>
<th scope="col">Email</th>
<th scope="col">Phone</th>
<th scope="col">Address</th>
<th scope="col">Description</th>
<th scope="col">Actions</th>
</tr>
</thead>
<tbody>
{customers && customers.map(customer =>
<tr key={customer.id}>
<td>{customer.first_name}</td>
<td>{customer.last_name}</td>
<td>{customer.email}</td>
<td>{customer.phone}</td>
<td>{customer.address}</td>
<td>{customer.description}</td>
<td>
<div className="d-flex justify-content-between align-items-center">
<div className="btn-group" style={{ marginBottom: "20px" }}>
<Link to={edit/${customer.id}} className="btn btn-sm btn-outline-secondary">Edit Customer </Link>
<button className="btn btn-sm btn-outline-secondary" onClick={() => this.deleteCustomer(customer.id)}>Delete Customer</button>
</div>
</div>
</td>
</tr>
)}
</tbody>
</table>
</div>
</div>
</div>
)
}
...

In this code block, you retrieve the lists of customers from the application's state as an array, iterate over it, and display it within an HTML table. You also add the customer.id parameter, which the method uses to identify and delete the details of a particular customer from the list.

Save and exit Home.tsx.

You've adopted a statically typed principle for all the components created with this application by defining types for the components and props through the use of interfaces. This is one of the best approaches to using TypeScript for a React application.

With this, you've finished creating all the required reusable components for the application. You can now update the app component with links to all the components that you have created so far.

Step 4 — Setting Up Routing and Updating the Entry Point of the Application

In this step, you will import the necessary components from the React Router package and configure the App component to render different components depending on the route that is loaded. This will allow you to navigate through different pages of the application. Once a user visits a route, for example /create, React Router will use the path specified to render the contents and logic within the appropriate component defined to handle such route.

Navigate to ./src/App.tsx:

nano App.tsx

Then replace its content with the following:

/src/App.tsx

import * as React from 'react';
import './App.css';
import { Switch, Route, withRouter, RouteComponentProps, Link } from 'react-router-dom';
import Home from './components/Home';
import Create from './components/customer/Create';
import EditCustomer from './components/customer/Edit';

class App extends React.Component<RouteComponentProps<any>> {
public render() {
return (
<div>
<nav>
<ul>
<li>
<Link to={'/'}> Home </Link>
</li>
<li>
<Link to={'/create'}> Create Customer </Link>
</li>
</ul>
</nav>
<Switch>
<Route path={'/'} exact component={Home} />
<Route path={'/create'} exact component={Create} />
<Route path={'/edit/:id'} exact component={EditCustomer} />
</Switch>
</div>
);
}
}
export default withRouter(App);

You imported all the necessary components from the React Router package and you also imported the reusable components for creating, editing, and viewing customers' details.

Save and exit App.tsx.

The ./src/index.tsx file is the entry point for this application and renders the application. Open this file and import React Router into it, then wrap the App component inside a BrowserRouter:

/src/index.tsx

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import { BrowserRouter } from 'react-router-dom';
import * as serviceWorker from './serviceWorker';
ReactDOM.render(
<BrowserRouter>
<App />
</BrowserRouter>
, document.getElementById('root')
);
serviceWorker.unregister();

React Router uses the BrowserRouter component to make your application aware of the navigation, such as history and current path.

Once you've finished editing Index.tsx, save and exit.

Lastly, you will use Bootstrap to add some style to your application. Bootstrap is a popular HTML, CSS, and JavaScript framework for developing responsive, mobile-first projects on the web. It allows developers to build an appealing user interface without having to write too much CSS. It comes with a responsive grid system that gives a web page a finished look that works on all devices.

To include Bootstrap and styling for your application, replace the contents of ./src/App.css with the following:

/src/App.css

@import 'https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css';

.form-wrapper {
width: 500px;
margin: 0 auto;
}
.App {
text-align: center;
margin-top: 30px;
}
nav {
width: 300px;
margin: 0 auto;
background: #282c34;
height: 70px;
line-height: 70px;
}
nav ul li {
display: inline;
list-style-type: none;
text-align: center;
padding: 30px;
}
nav ul li a {
margin: 50px 0;
font-weight: bold;
color: white;
text-decoration: none;
}
nav ul li a:hover {
color: white;
text-decoration: none;
}
table {
margin-top: 50px;
}
.App-link {
color: #61dafb;
}
@keyframes App-logo-spin {
from {
transform: rotate(0deg);
}
to {
transform: rotate(360deg);
}
}

You have used Bootstrap here to enhance the look and feel of the application by giving it a default layout, styles, and color. You have also added some custom styles, particularly to the navigation bar.

Save and exit App.css.

In this section, you have configured React Router to render the appropriate component depending on the route visited by the user and also added some styling to make the application more attractive to users. Next, you will test all the functionality implemented for the application.

Step 5 — Running Your Application

Now that you have set up the frontend of this application with React and TypeScript by creating several reusable components, and also built a REST API with the json-server, you can run your app.

Navigate back to the project’s root folder:

cd ~/typescript-react-app

Next run the following command to start your app:

yarn start

Note: Make sure your server is still running in the other terminal window. Otherwise, start it with: yarn server.

Navigate to http://localhost:3000 to view the application from your browser. Then proceed to click on the Create button and fill in the details of a customer.

After entering the appropriate values in the input fields, click on the Create Customer button to submit the form. The application will redirect you back to your homepage once you're done creating a new customer.

Click the Edit Customer button for any of the rows and you will be directed to the page that hosts the editing functionality for the corresponding customer on that row.

Edit the details of the customer and then click on Edit Customer to update the customer’s details.

You've run your application to ensure all the components are working. Using the different pages of your application, you've created and edited a customer entry.

Conclusion

In this tutorial you built a customer list management app with React and TypeScript. The process in this tutorial is a deviation from using JavaScript as the conventional way of structuring and building applications with React. You've leveraged the benefits of using TypeScript to complete this front-end focused tutorial.

To continue to develop this project, you can move your mock back-end server to a production-ready back-end technology like Express or Nest.js. Furthermore, you can extend what you have built in this tutorial by adding more features such as authentication and authorization with different tools like the Passport.js authentication library.

Thank you for reading!

JavaScript developers should you be using Web Workers?

JavaScript developers should you be using Web Workers?

Do you think JavaScript developers should be making more use of Web Workers to shift execution off of the main thread?

Originally published by David Gilbertson at https://medium.com

So, Web Workers. Those wonderful little critters that allow us to execute JavaScript off the main thread.

Also known as “no, you’re thinking of Service Workers”.

Photo by Caleb Jones on Unsplash

Before I get into the meat of the article, please sit for a lesson in how computers work:

Understood? Good.

For the red/green colourblind, let me explain. While a CPU is doing one thing, it can’t be doing another thing, which means you can’t sort a big array while a user scrolls the screen.

This is bad, if you have a big array and users with fingers.

Enter, Web Workers. These split open the atomic concept of a ‘CPU’ and allow us to think in terms of threads. We can use one thread to handle user-facing work like touch events and rendering the UI, and different threads to carry out all other work.

Check that out, the main thread is green the whole way through, ready to receive and respond to the gentle caress of a user.

You’re excited (I can tell), if we only have UI code on the main thread and all other code can go in a worker, things are going to be amazing (said the way Oprah would say it).

But cool your jets for just a moment, because websites are mostly about the UI — it’s why we have screens. And a lot of a user’s interactions with your site will be tapping on the screen, waiting for a response, reading, tapping, looking, reading, and so on.

So we can’t just say “here’s some JS that takes 20ms to run, chuck it on a thread”, we must think about where that execution time exists in the user’s world of tap, read, look, read, tap…

I like to boil this down to one specific question:

Is the user waiting anyway?

Imagine we have created some sort of git-repository-hosting website that shows all sorts of things about a repository. We have a cool feature called ‘issues’. A user can even click an ‘issues’ tab in our website to see a list of all issues relating to the repository. Groundbreaking!

When our users click this issues tab, the site is going to fetch the issue data, process it in some way — perhaps sort, or format dates, or work out which icon to show — then render the UI.

Inside the user’s computer, that’ll look exactly like this.

Look at that processing stage, locking up the main thread even though it has nothing to do with the UI! That’s terrible, in theory.

But think about what the human is actually doing at this point. They’re waiting for the common trio of network/process/render; just sittin’ around with less to do than the Bolivian Navy.

Because we care about our users, we show a loading indicator to let them know we’ve received their request and are working on it — putting the human in a ‘waiting’ state. Let’s add that to the diagram.

Now that we have a human in the picture, we can mix in a Web Worker and think about the impact it will have on their life:

Hmmm.

First thing to note is that we’re not doing anything in parallel. We need the data from the network before we process it, and we need to process the data before we can render the UI. The elapsed time doesn’t change.

(BTW, the time involved in moving data to a Web Worker and back is negligible: 1ms per 100 KB is a decent rule of thumb.)

So we can move work off the main thread and have a page that is responsive during that time, but to what end? If our user is sitting there looking at a spinner for 600ms, have we enriched their experience by having a responsive screen for the middle third?

No.

I’ve fudged these diagrams a little bit to make them the gorgeous specimens of graphic design that they are, but they’re not really to scale.

When responding to a user request, you’ll find that the network and DOM-manipulating part of any given task take much, much longer than the pure-JS data processing part.

I saw an article recently making the case that updating a Redux store was a good candidate for Web Workers because it’s not UI work (and non-UI work doesn’t belong on the main thread).

Chucking the data processing over to a worker thread sounds sensible, but the idea struck me as a little, umm, academic.

First, let’s split instances of ‘updating a store’ into two categories:

  1. Updating a store in response to a user interaction, then updating the UI in response to the data change
  2. Not that first one

If the first scenario, a user taps a button on the screen — perhaps to change the sort order of a list. The store updates, and this results in a re-rendering of the DOM (since that’s the point of a store).

Let me just delete one thing from the previous diagram:

In my experience, it is rare that the store-updating step goes beyond a few dozen milliseconds, and is generally followed by ten times that in DOM updating, layout, and paint. If I’ve got a site that’s taking longer than this, I’d be asking questions about why I have so much data in the browser and so much DOM, rather than on which thread I should do my processing.

So the question we’re faced with is the same one from above: the user tapped something on the screen, we’re going to work on that request for hopefully less than a second, why would we want to make the screen responsive during that time?

OK what about the second scenario, where a store update isn’t in response to a user interaction? Performing an auto-save, for example — there’s nothing more annoying than an app becoming unresponsive doing something you didn’t ask it to do.

Actually there’s heaps of things more annoying than that. Teens, for example.

Anyhoo, if you’re doing an auto-save and taking 100ms to process data client-side before sending it off to a server, then you should absolutely use a Web Worker.

In fact, any ‘background’ task that the user hasn’t asked for, or isn’t waiting for, is a good candidate for moving to a Web Worker.

The matter of value

Complexity is expensive, and implementing Web Workers ain’t cheap.

If you’re using a bundler — and you are — you’ll have a lot of reading to do, and probably npm packages to install. If you’ve got a create-react-app app, prepare to eject (and put aside two days twice a year to update 30 different packages when the next version of Babel/Redux/React/ESLint comes out).

Also, if you want to share anything fancier than plain data between a worker and the main thread you’ve got some more reading to do (comlink is your friend).

What I’m getting at is this: if the benefit is real, but minimal, then you’ve gotta ask if there’s something else you could spend a day or two on with a greater benefit to your users.

This thinking is true of everything, of course, but I’ve found that Web Workers have a particularly poor benefit-to-effort ratio.

Hey David, why you hate Web Workers so bad?

Good question.

This is a doweling jig:

I own a doweling jig. I love my doweling jig. If I need to drill a hole into the end of a piece of wood and ensure that it’s perfectly perpendicular to the surface, I use my doweling jig.

But I don’t use it to eat breakfast. For that I use a spoon.

Four years ago I was working on some fancy animations. They looked slick on a fast device, but janky on a slow one. So I wrote fireball-js, which executes a rudimentary performance benchmark on the user’s device and returns a score, allowing me to run my animations only on devices that would render them smoothly.

Where’s the best spot to run some CPU intensive code that the user didn’t request? On a different thread, of course. A Web Worker was the correct tool for the job.

Fast forward to 2019 and you’ll find me writing a routing algorithm for a mapping application. This requires parsing a big fat GeoJSON map into a collection of nodes and edges, to be used when a user asks for directions. The processing isn’t in response to a user request and the user isn’t waiting on it. And so, a Web Worker is the correct tool for the job.

It was only when doing this that it dawned on me: in the intervening quartet of years, I have seen exactly zero other instances where Web Workers would have improved the user experience.

Contrast this with a recent resurgence in Web Worker wonderment, and combine that contrast with the fact that I couldn’t think of anything else to write about, then concatenate that combined contrast with my contrarian character and you’ve got yourself a blog post telling you that maybe Web Workers are a teeny-tiny bit overhyped.

Thanks for reading

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Further reading

An Introduction to Web Workers

JavaScript Web Workers: A Beginner’s Guide

Using Web Workers to Real-time Processing

How to use Web Workers in Angular app

Using Web Workers with Angular CLI