How to isolate critical CSS when using Create React App

What is the best way to address render blocking CSS and only loading critical CSS with Create React App since there is no access to edit the webpack config file?

What is the best way to address render blocking CSS and only loading critical CSS with Create React App since there is no access to edit the webpack config file?

Setting up Reactjs using Webpack 4 and Babel 7

Setting up Reactjs using Webpack 4 and Babel 7

In this tutorial we will be setting up our very own reactjs from scratch using webpack and babel, so grab your pen and paper lets spin the learning wheel.

In this tutorial we will be setting up our very own reactjs from scratch using webpack and babel, so grab your pen and paper lets spin the learning wheel.

Almost everyone who started out to learn reactjs was introduced to create-react-app, which is an awesome way to bootstrap any reactjs project. We were happy with it since you can just run a simple command, then boom your reactjs app development is ready. But at some point in your career you'd want to configure everything from scratch to fit a particular purpose.

Table of Contents

  • Setting up the Project
  • Setting up Webpack
  • Setting up Babel
  • Setting up React
  • Connecting React Component to the DOM
  • Finishing Touches
  • Conclusion
Setting up the Project

Before you can get started, you should make sure to have an installed editor and terminal on your machine. In addition, you will need an installed version of node with npm. Make sure to have setup everything of it before you continue to read.

Before we start writing any code, lets create a new directory where our project will stay. In any location on your computer, run the following in your terminal

mkdir webpack-babel-react-starter
cd webpack-babel-react-starter

We need to initialise our project with a package.json file, since we are going to install some packages that is vital for the setup. Simply run yarn init -y

For this tutorial i will be making use of yarn as my package manager, if you are using npm, make sure you run the corresponding command, it should work as expected.

Setting up Webpack

Webpack is one of the most popular bundler out there. It internally builds a dependency graph when it processes your application, this graph maps every module your project needs and generates one or more bundles. Since version 4.0.0, webpack does not require a configuration file to bundle your project, nevertheless it is incredibly configurable to better fit your needs.

let's install it by running:

yarn add webpack --dev

We also need to install the webpack cli

yarn add webpack-cli --dev

After installing this two packages, you will notice a new addition in our project, the node_modules and devDependencies section in our package.json file. Next thing to do is to add the webpack you just install into the package.json file.

"scripts": {
  "build": "webpack --mode production"
}

At this point you don't really need a configuration file to get started, which is a cool addition to webpack 4

Setting up Babel

Modern javascript is written in ES6 or ES7, but not every browser understands this modern javascript, it's at this juncture we need babel to do the heavy lighting for us. Babel is a tool-chain that is mainly used to convert ECMAScript 2015+ code into a backwards compatible version of JavaScript in current and older browsers or environments. Checkout there docs for more info about what they can do for you.

React components are mostly written in ES6, with the concept of imports, class and other ES6+ features, which older browsers do not understand. Webpack on it's own does not know how to transform or better still transpile the ES6 code to ES5 code. But their is hope for us, webpack have this concept of loaders, a webpack loader takes something as the input and produces something else as the output.

For our setup, we will use babel-loader which is webpack loader that will transpile our ES6 code for us. Before we start using babel-loader, we need to install some packages and setup babel preset env which will target the particular javascript version we want to transpile to.

let's install all the dependencies:

yarn add @babel/core @babel/preset-env @babel/preset-react babel-loader --dev

We also need to setup our babel config file, create a new file in the root directory called .babelrc and write the following configuration to it

{
  "presets": ["@babel/env", "@babel/react"]
}

The above configuration will ensure that babel transpiles our react code, which is JSX and any other ES6+ code we have to ES5 code.

Now is the perfect time to create a minimal webpack configuration for our project. Create a webpack.config.js file in the root directory and write the following configuration for it

module.exports = {
  module: {
    rules: [
      {
        test: /.(js|jsx)$/,
        exclude: /node_modules/,
        use: {
          loader: "babel-loader"
        }
      }
    ]
  }
}

What the above configuration does is that for every file with a js or jsx extension, excluding the node_modules folder and it's content, webpack uses babel-loader to transpile the ES6 code to ES5. With this done, lets head over to writing our react component.

Setting up React

We will be creating a very simple react component, that renders a text and a button, but in order to make use of react we need to install some dependencies, react and react-dom .

yarn add react react-dom

After installing those, create a new folder in the root directory, let's call it src inside it create index.js file

In the index.js file write the following code:

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

const Index = () => {
  return (
    
      
        
          React Page {" "}
        
        

        <a
          className="button-line"
          href="https://github.com/deityhub"
          target="_blank"
        >
          Know more
        
      
    
  );
};

export default Index;

It's time to test things out and see how powerful webpack is. Open up your terminal once again and run

yarn run build

If it's successful you should see a dist folder created for us by webpack, and inside it is an index.js file which have minified version of our ES5 code. Why is the code minified, if you remember in our build script in package.json we specified a --mode production flag after the webpack command, under the hood, webpack will generate a minified version of our ES5 code. To see a readable format of the transpiled code, you can swap the --mode production with --mode development

Yay!, the output was great but that's not what we really want for our react app, we want our transpiled code to be visible in our browser. So let's setup html and also css(scss) to work with our webpack.

Connecting React Component to the DOM

We need to setup an html file so that our react component can be rendered on the dom, but we can't just create a random html file and hook up our react to it using react dom. So to achieve this we need to install the package html-webpack-plugin

yarn add html-webpack-plugin --dev

Adjust your webpack.config.js file to look like this

const path = require("path");
const HtmlWebpackPlugin = require("html-webpack-plugin");

module.exports = {
  entry: path.join(__dirname, "src", "index.js"),
  output: {
    path: path.join(__dirname, "build"),
    filename: "bundle.js"
  },
  module: {
    rules: [
      {
        test: /.(js|jsx)$/,
        exclude: /node_modules/,
        use: {
          loader: "babel-loader"
        }
      }
    ]
  },
  plugins: [
    new HtmlWebpackPlugin({
      filename: "index.html",
      template: path.join(__dirname, "src", "index.html")
    })
  ]
};

If you notice, we are adjusting the input and output so we have a bit more control over the naming and target of our files.

Nextup is to create an html file inside src folder, let's call it index.html and then paste the following code into it



  
    
    
    React, Webpack, Babel Starter Pack
    
  
  
     You need to enable JavaScript to run this app. 
    
    

  

Since we are in the src let's make some adjustments to our react component, first we create a new folder components then inside this folder a two files app.js and app.scss then make this following adjustments to our code:

In ./src/index.js

import React from "react";
import ReactDOM from "react-dom";
import App from "./components/app";

ReactDOM.render(, document.getElementById("app"));

In ./src/components/app.js

import React from "react";
import "./app.scss";

const App = () => {
  return (
    
      
        
          React Page {" "}
        
        

        <a
          className="button-line"
          href="https://github.com/deityhub"
          target="_blank"
        >
          Know more now
        
      
    
  );
};

export default App;

In ./src/components/app.scss

body {
  background: linear-gradient(253deg, #0cc898, #1797d2, #864fe1);
  background-size: 300% 300%;
  -webkit-animation: Background 25s ease infinite;
  -moz-animation: Background 25s ease infinite;
  animation: Background 25s ease infinite;
}

.full-screen {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
//you need to setup file-loader in webpack before you can use images
  background: url("../../assests/image/background.png");
  background-size: cover;
  background-position: center;
  width: 100%;
  height: 100%;
  display: -webkit-flex;
  display: flex;
  -webkit-flex-direction: column;
  //_ works with row or column_

  flex-direction: column;
  -webkit-align-items: center;
  align-items: center;
  -webkit-justify-content: center;
  justify-content: center;
  text-align: center;
}

h1 {
  color: #fff;
  font-family: "Open Sans", sans-serif;
  font-weight: 800;
  font-size: 4em;
  letter-spacing: -2px;
  text-align: center;
  text-shadow: 1px 2px 1px rgba(0, 0, 0, 0.6);

  &:after {
    display: block;
    color: #fff;
    letter-spacing: 1px;
    font-family: "Poiret One", sans-serif;
    content: "React project powered by webpack and babel with support for sass";
    font-size: 0.4em;
    text-align: center;
  }
}

.button-line {
  font-family: "Open Sans", sans-serif;
  text-transform: uppercase;
  letter-spacing: 2px;
  background: transparent;
  border: 1px solid #fff;
  color: #fff;
  text-align: center;
  font-size: 1.4em;
  opacity: 0.8;
  padding: 20px 40px;
  text-decoration: none;
  transition: all 0.5s ease;
  margin: 0 auto;
  display: block;

  &:hover {
    opacity: 1;
    background-color: #fff;
    color: grey;
  }
}

@-webkit-keyframes Background {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}

@-moz-keyframes Background {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}

@keyframes Background {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}

We will be adding some styling in addition to the html and react component that we will render in the dom. So before we run our code to test it, we need to configure our webpack so it will know how to handle any .css or .scss file being passed through it.

yarn add css-loader sass-loader mini-css-extract-plugin node-sass --dev

sass-loader being installed here is used by webpack to convert our .scss to a .css file that the browser understands, and under the hood it makes use of node-sass to achieve this. Then mini-css-extract-plugin as the name suggests, abstract all our css files into a single css file, instead of the normal behaviour that webpack offers, which is to bundle your css file with the final .js output file which then injects the css into your rendered html output when you run the code.

Open up your webpack config file and adjust your code to look like this

const path = require("path");
const HtmlWebpackPlugin = require("html-webpack-plugin");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");

module.exports = {
  entry: path.join(__dirname, "src", "index.js"),
  output: {
    path: path.join(__dirname, "build"),
    filename: "bundle.js"
  },
  module: {
    rules: [
      {
        test: /.(js|jsx)$/,
        exclude: /node_modules/,
        use: {
          loader: "babel-loader"
        }
      },
      {
        test: /.(css|scss)$/,
        use: [MiniCssExtractPlugin.loader, "css-loader", "sass-loader"]
      }
    ]
  },
  plugins: [
    new HtmlWebpackPlugin({
      filename: "index.html",
      template: path.join(__dirname, "src", "index.html")
    }),
    new MiniCssExtractPlugin({
      filename: "[name].css",
      chunkFilename: "[id].css"
    })
  ]
};

There is a point to note here, the order of your loaders in the webpack config file matters a lot, because webpack processes the loaders from right to left. So using the test for css files for example, it will run sass-loader first, then css-loader and finally MiniCssExtractPlugin.

There is one more thing to do, let's install webpack dev server, this will create a development server for us and monitor our files for any changes during development.

yarn add webpack-dev-server --dev

Then open your package.json file and make the following adjustments in your scripts tag

"scripts": {
    "start": "webpack --mode development",
    "dev": "webpack-dev-server --mode development --open",
    "build": "webpack --mode production"
  }

That's to much code right?, so let's test our code by running yarn run dev

if everything went well, you should see something like this on your browser.

Finishing Touches

If you followed this tutorial step by step, I'm quite confident that you will end up knowing and mastering the usage of webpack and babel. Going forward i want us to add two more features to this project, just to demonstrate that you can extend or add more features tomorrow when working on a more advanced react project than this.

Open your terminal and install this packages

yarn add file-loader @babel/plugin-proposal-class-properties --dev

file-loader will handle all the scenario where we want to import an image or an svg or even a gif while @babel/plugin-proposal-class-properties will handle react class components and static class properties.

In webpack.config.js adjust it to look like this

const path = require("path");
const HtmlWebpackPlugin = require("html-webpack-plugin");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");

module.exports = {
  entry: path.join(__dirname, "src", "index.js"),
  output: {
    path: path.join(__dirname, "build"),
    filename: "bundle.js"
  },
  module: {
    rules: [
      {
        test: /.(js|jsx)$/,
        exclude: /node_modules/,
        use: {
          loader: "babel-loader"
        }
      },
      {
        test: /.(css|scss)$/,
        use: [MiniCssExtractPlugin.loader, "css-loader", "sass-loader"]
      },
      {
        test: /.(jpg|jpeg|png|gif|mp3|svg)$/,
        use: [
          {
            loader: "file-loader",
            options: {
              name: "[path][name]-[hash:8].[ext]"
            }
          }
        ]
      }
    ]
  },
  plugins: [
    new HtmlWebpackPlugin({
      filename: "index.html",
      template: path.join(__dirname, "src", "index.html")
    }),
    new MiniCssExtractPlugin({
      filename: "[name].css",
      chunkFilename: "[id].css"
    })
  ]
};

In .babelrc file, also adjust it to look like this

{
  "presets": ["@babel/env", "@babel/react"],
  "plugins": ["@babel/plugin-proposal-class-properties"]
}

Finally run yarn run dev to make sure everything is stile working.

Conclusion

If you made it thus far, congratulation you deserve a pizza, because not everybody that started out to learn something new eventually completes it. I want you to work on what you've learnt in this tutorial, extend the configuration and build something awesome from it. You can checkout the github link to the complete code.

Thanks for reading

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URLs and Webpack in Reactjs

URLs and Webpack in Reactjs

URLs and Webpack in Reactjs - I am still a newbie in ReactJS. I've been following series of tutorials and articles on the framework and decided to start putting what I've learnt so far into practice.

My website, dillionmegida.com was built with PHP. You could check it out as I highly appreciate reviews. I'm though aspiring to be a full-stack javascript developer so I'm in some way trying to depart from PHP :)

I decided to replicate my homepage using React and to broaden my skills in using components.

It was going quite successful until I tried using an <img> JSX element. I used it like;

import React from 'react'
 
let dpStyle = {
    // Some styles
}
 
let Profilepic = () => (
    <div className={dpStyle}>
        <img src='../img/deee.jpeg' alt='My profile picture'/>
    </div>
)
export default Profilepic;

The img folder was a sub-directory of the src folder.

My aim here was to have my profile picture as a component with some styling to be used on my homepage and any other desired page. The src for the img tag was not been used appropriately as my image was not displayed.

I paused to think of the problem, inspected my page and discovered the src displayed there was exactly as I inputted it. So silly of me :( I made some researches which helped me remember that most attributes of JSX element are not as mostly used with HTML, but have to be enclosed in curly braces.

import React from 'react'
 
let dpStyle = {
    // Some styles
}
 
let Profilepic = () => (
    <div className={dpStyle}>
        <img src={'../img/deee.jpeg'} alt='My profile picture'/>
    </div>
)
export default Profilepic;

I tried rendering the page again and my image was still not displayed.

Funny enough, I quickly thought of a trick (for the first time);

...
import Dp from '../img/deee.jpeg'
...
let Profilepic = () => (
    <div className={dpStyle}>
        <img src={Dp} alt='My profile picture'/>
    </div>
)

To my amazement, it worked. I was excited and at the same time sad, with feeling of little guilt. I didn't know why. lol. I said to myself, 'I am not doing the right thing :(' and also asked myself, 'Is react as crazy as this?'

I headed back to google to make some more research and got to discover that the webpack that React (create-react-app) automatically installed had been configured to use the public folder (at the same level with src folder) for relative URLs (such as my image URL).

Using ...<img src={'../img/deee.jpeg'} />..., React was actually checking the public folder for the image sub-directory which it couldn't find.

Solution

1. Change the location of the image folder

I changed the location of the image folder making it a sub-directory under the public directory and it worked as expected.

2. Use the require keyword

Just as the import keyword is used for relative URLs, the require keyword does same. So, I was able to do this;

import React from 'react'
 
let dpStyle = {
    // Some styles
}
 
let Profilepic = () => (
    <div className={dpStyle}>
        <img src={require('../img/deee.jpeg')} alt='My profile picture'/>
    </div>
)
export default Profilepic;

and in the other pages where the Profilepic component was required and used, my image displayed perfectly. :D

Like I said, I am still a newbie at ReactJS but I hope this little experience would be helpful for you too. There are other super powers of webpacks too which I would still be learning. Please do share in the comment section corrections on this article and also helpful Tips.

I'll be documenting my experience in my ReactJS journey as much as I can. Stay tuned and thanks for reading.

Originally published by Megida Dillion at dillion.hashnode.dev

=======================================================

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Css is not used by jsx in ReactJS

I use ReactJS with Webpack and TypeScript. I'm trying to include CSS with React. But my CSS is not use by my React application. I created a global.d.ts file to declare my css module. I imported my css into my.tsx file but when I add a class to an element, nothing works.

I use ReactJS with Webpack and TypeScript. I'm trying to include CSS with React. But my CSS is not use by my React application. I created a global.d.ts file to declare my css module. I imported my css into my.tsx file but when I add a class to an element, nothing works.

I have already tried to install a css module but I didn't succeed. So, I just made the solution to create a global.d.ts file

global.d.ts :

declare module '*.css';

Hello.tsx

import * as css from './Hello.css';

export interface HelloProps {
compiler: string;
framework: string;
}

export class Hello extends React.Component<HelloProps, {}> {

render() {
return (
<form>
<p className={css.test}> Test </p>
</form>
);
}
}

Hello.css


.test {
color: red;
}

webpack.config.js

module: {
rules: [

 .....

 { test: /\.css$/, exclude: /node_modules/, use: ['style-loader', 'css-loader'] }

]
},

The word "test" is written in black. When it should be in red