How to create a React app from scratch
Using Webpack4.

First, we need to create our app folder.

mkdir  reactscratch
cd     reactscratch
npm init // intializing package.json file

They are a lot of packages need to install so that

Open your package.json file and paste the below code and save it.

Now in your terminal paste the below command so that project
dependencies installed

npm i // i for install

I will explain later what these packages are doing.

Now create a webpack.config.js file in your directory. and paste below code

module.exports={
    entry:{
     index:'./src/index.js',
    },

  output: {
      path: path.resolve(__dirname, 'dist'),
      filename: 'bundle.js',
      chunkFilename:'[id][hash].js',
      publicPath:'/'
    },

}

Because we need to tell the webpack entry point and output .

entry Point: The entry point is index.js so that it takes all
required imports and exports from index.js and outputs
it in the dist folder naming bundle.js file.

But webpack does more it takes code from the index.js and applies some
transformations, for example, converting es6 to es5.

Now let's add our transformations to our webpack config file

module: {
        rules: [

          {
            test: /\.(js|jsx)$/,
            exclude: /(node_modules|bower_components)/,
            use:['babel-loader']

          }
    ]
}

What above code does is it checks if any file ends with .js/.jsx
send that files to the babel-loader and apply transformations.

Like we are using jsx but our browser doesn't understand jsx so that
babel loader takes our jsx and converted it into javascript.

They are different types of loaders avaiable css-loader style-loader file-loader ,html-loader.

We can add more loaders in rules array now I'm showing how to add css-loader

  {
            test:/\.css$/, use:[
           {loader:"css-loader",
              options:{
                minimize:true,
                sourceMap:true
              }
   }

css-loader: goes through possible @import and url() lookups within the matched files and creates source map for our CSS files, compress the css files by removing white spaces.

Webpack offers us plugins they are different types of plugins
available.

let's use plugins now

 new MiniCssExtractPlugin({
      filename: "[name]-[hash].css",
      chunkFilename: "[id][hash].css"
    })

This plugin extracts CSS into separate files. It creates a CSS file per JS file which contains CSS. It supports On-Demand-Loading of CSS and SourceMaps.

[name]:it indicates the name of the css file we created in our projected.
[hash]:webpack adds some random hash code.

Now you have some understanding about what webpack does

This is our final webpack.config.js file

With these our webpack custom setup is completed.

But we are not created any js/html/css yet.

I'm using the above folder structure.

Create the index.html file in public folder

In our web pack config file, we are already pointing to this HTML file.

Template: We are entering the path where our HTML file is located.
inject: it is optional actually what it does is Inject the script files inside the body tag.

In src folder, we can create react components now

for example app.js

import React from 'react';
import './app.css';
import img from '../public/assets/download.png'

class App extends React.Component{
    render(){
        return(
            <div className="app">
             <h1>Hello React</h1>
               <img src={img} className="img"/>

            </div>
        )
    }
}
export default App;

Let's create an index.js file now in src folder why because we are using entry point as index.js in our webpack config file.

import React from 'react';
import ReactDom from 'react-dom';
import App from './app';

ReactDom.render(<App/>,document.getElementById('root'))

npm start // to run the webpack development server

It should be something like above image.

If you need a code for the production run npm run build

webpack creates a dist folder with required files.

Now you have some great understanding about webpack and loaders.

If you want to add routing and lazyloading I will be will show it in my
next post

CODE REPOSITORY.

Resources

• Webpack docs

• Webpack Plugins

• Webpack loaders

If you want to know about react in lower level check out my post

Explaining 🐘React like I don't know anything