Introduction to WebPack

I studied several times, but I still forgot every time. I made notes while studying to deepen my impression.

1. Webpack profile

Description: Webpack is a static module packaging tool for modern JavaScript applications. When WebPack works with an application, it internally builds a dependency graph that maps to each module required for the project and generates one or more bundles.

2. Five core concepts of Webpack

2.1 Entry

The Entry indicates which file webPack starts packing as the Entry point, analyzing and building the internal dependency diagram

2.2 the Output

Output indicates where the Output of the resource bundles packaged by Webapck goes and how to name them.

2.3 Loader

Loader enables Webpack to handle non-javascript files (Webpack itself only understands Javascript)

3.3 the Plugins

Plugins can be used to perform a wider range of tasks, from packaging optimization and compression to redefining variables in a new environment.

3.4 Mode

Mode instructs Webpack to use the configuration of the corresponding Mode. By selecting one of development, Production, or None to set the mode parameter, you can enable the optimizations built into WebPack for that environment. The default value is production.

3. Webpack early experience

3.1 Initializing the Project

Enter in the command window

npm init
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Initialize the project and fill in the relevant information as required. I didn’t fill in any information here

3.2 Installation Dependencies

Run the command to install dependencies globally

npm i webpack  webpack-cli -g
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Run the command to install it locally

npm i webpack  webpack-cli -D
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Create a directory structure as shown in the following figure

SRC stores resource files. Index.js webpack entry starting point file; Build as the output directory of the packaged files;

Enter it in the index.js file

function add(x, y) {
  return x + y;
}
console.log(add(1.2));
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Execute the following commands on the command line, respectively, to see the differences in the packaged build output file

Webpack. / SRC/index.js-o./build --mode=productionCopy the code

conclusion

Webpack can handle JS/JSON resources, not CSS/IMG resources
Production and development environments compile ES6 modules into modularity that browsers recognize
The production environment has one more compressed JS code than the development environment

Configure CSS styles and static resources

4. Package style resources

Create demo. The file structure is as follows

Package style resources requiredCSS - loader, the style - loaderTwo dependencies. Download the dependencies and execute the following command

npm i  css-loader  style-loader  -D
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Configure the webpack.config.js configuration file

// It is mainly used to write the configuration automatic prompt, but it needs to be annotated when repackaging, otherwise an error will be reported
// import { Configuration } from "webpack";

const { resolve } = require("path");
/ * * *@type {Configuration}* /
const config = {
  entry: "./src/index.js".output: {
    filename: "build.js".path: resolve(__dirname, "build"),},module: {
    rules: [{test: /\.css$/,
        use: [
          // Use Loaders in data are executed in sequence
          "style-loader"."css-loader",],},],},plugins: [].mode: "development"};module.exports = config;
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In the index.css file, the HTML, body tag provides a style, and the index.js file is introduced

index.css

html.body{
    background-color: pink;
}
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index.js

import "./index.css";
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After the configuration is complete, run the webpack command.

webpack
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After the package is completed, we need to test whether the style file is successfully packaged. In the build folder, create an index. HTML file and import the packed build.js file. When you open the page in your browser, the style file has taken effect.

But in our development process, instead of using CSS style files, we might use less sass style files, so what should we do?

We just need to add the rules for less and sass to the rules in the module in webpack.config.js. Here, take less as an example.

The installationLess - loader, lessRely on
Add rules rules

 {
    test: /\.less$/,
    use: ["style-loader"."css-loader"."less-loader"],}Copy the code

Index. less imports into the index.js file
performwebpackThe command

Has to take effect

5. Package HTML resources

Create demo. The structure is as follows

The installationhtml-webpack-pluginPlugin.

npm i html-webpack-plugin -D
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Configure webpack.config.js as follows

Add the following

const HtmlWepackPlugin = require("html-webpack-plugin");

plugins: [
    new HtmlWepackPlugin({
      // copy the "./ SRC /index.html" file
      template: "./src/index.html",})],Copy the code

Complete configuration

// import { Configuration } from "webpack";
const { resolve } = require("path");
const HtmlWepackPlugin = require("html-webpack-plugin");

/ * * *@type {Configuration}* /
const config = {
  entry: "./src/index.js".output: {
    filename: "build.js".path: resolve(__dirname, "build"),},module: {
    rules: []},plugins: [
    new HtmlWepackPlugin({
      // copy the "./ SRC /index.html" file
      template: "./src/index.html",})],mode: "development"};module.exports = config;
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Execute pack commandwebpack

6. Pack your photo resources

The demo file structure is as follows:

Packaging image resources requires installationUrl - loader, file - loaderInstall the url – loader

npm  i url-loader file-loader -D
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Configure the webpack.config.js file and add the following rules to rules

{
    test: /\.(jpg|png|gif)$/,
    loader: "url-loader".options: {
      // Images smaller than 8KB are base64 processed
      limit: 8 * 1024.// Rename the image
      // image Prints images to the images folder
      // [name] the original name of the image
      // [hash:10] Takes the first 10 digits of the image hash
      // [ext] takes the original extension of the image
      name: "images/[name].[hash:10].[ext]",}},Copy the code

Add styles to the index.less file and import images. Import the index.js file
Run the webpack command, and the result is as follows: The packed image resources have taken effect

The packing results are also executed as we set them up

If we write an IMG tag to an HTML page, we will not be able to package it as described above, so we need to configure webpack.config.js

The installationhtml-loader

npm i html-loader -D
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Configuration rules

  {
    test: /\.html$/.// Process the IMG image in HTML (import img to urL-loader for processing)
    loader: "html-loader".options: {
      // Because url-loader uses ES6 modularized parsing by default, htMl-loader uses commonJS to parse images
      // Disable THE ES6 modularization of url-loader and use commonJS parsing
      esModule: false,}},Copy the code

Re-execute the package command, and the IMG tag written in the HTML page is displayed

Note that we need to turn off the esModule, because because url-loader uses ES6 modular parsing by default and htMl-loader introduces images, there will be problems with commonJS parsing and images will not be displayed

7. Configuration devserver

When writing or modifying the code in the environment we configured before, we need to re-pack the webpack after each modification, and then open the packed HTNL file in the browser, which is very inconvenient, so we need to configure DevServer here

To install devServer, run the following command

npm i  webpack-dev-server -D
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Add the following code to webpack.config.js

devServer: {
    // Project build path
    contentBase: resolve(__dirname, "build"),
    // Start gzip compression
    compress: true./ / the port number
    port: 3000.// Automatically open the browser
    open: true,},Copy the code

Execute the commandnpx webpack serverOn startup, we can see that the page opens in the default browser, and a port 3000 is launched,http://localhost:3000You can see our results.

We modify the code after saving the code will be automatically edited, and automatically refresh the page, so that more efficient coding

8. Extract CSS styles into separate style files

The previous configuration, the packaged CSS style code is all in the JS file, now we need to separate the CSS into a CSS file

Create new A.css and b.css files, write styles respectively, and introduce style files in index.js. Structure is as follows

The installationmini-css-extract-pluginThe plug-in

npm i mini-css-extract-plugin -D
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Configuration webpack. Config. Js

To obtainMiniCssExtractPlugin

const MiniCssExtractPlugin = require("mini-css-extract-plugin");
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You need tostyle-loaderreplaceMiniCssExtractPlugin.loader

use: [
      // "style-loader",
      // Replace style-loader to extract CSS files as separate files
      MiniCssExtractPlugin.loader,
      "css-loader",].Copy the code

Add the plug-inMiniCssExtractPlugin

plugins: [
    new HtmlWebpackPlugin({
      template: "./index.html",}).new MiniCssExtractPlugin({
      filename: "css/build.css",})],Copy the code

Execute the package command, the package result is as follows, the CSS style file is extracted to build.css

9. CSS compatibility

In front-end development, we may encounter a variety of browsers and different browser versions, so we need to adapt our CSS to all browser versions.

Installing a plug-in

npm i postcss-loader postcss-preset-env  -D
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Configuration webpack. Config. Js

addpostcss-loader

/** * CSS compatibility handling: Postcss -->postcss-loader postCSs-preset -env * Help PostCSS find the configuration in package.json browserList and load the specified CSS compatibility */
// Use the default loader location
// 'postcss-loader,

// Change the loader location
{
loader: "postcss-loader".options: {
  postcssOptions: {
    ident: "postcss"./ / postcss plug-in
    plugins: [require("postcss-preset-env")],}}},Copy the code

Add it in package.jsonbrowserslist

 "browserslist": {
    "development": [
      "last 1 chrome version"."last 1 firefox version"."last 1 safari version"]."production": [
      "0.2%" >."not dead"."not op_mini all"]}Copy the code

Add cSS3 properties to the CSS to test whether the PostCSS compatibility takes effect
Check whether compatibility properties are added to the CSS3 properties in the build. CSS package

10. CSS compression

The installationoptimize-css-assets-webpack-plugin

 npm i optimize-css-assets-webpack-plugin  -D
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Configuration webpack. Config. Js

const OptimizeCssAssetsWebpackPlugin = require("optimize-css-assets-webpack-plugin");

 plugins: [
    new OptimizeCssAssetsWebpackPlugin(),
 ],

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Complete webpack.config.js configuration

//import { Configuration } from "webpack";

const { resolve } = require("path");

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

// process.env.NODE_ENV = "development";

//optimize-css-assets-webpack-plugin

/ * * *@type {Configuration}* /
const config = {
  entry: "./src/js/index.js".output: {
    filename: "js/build.js".path: resolve(__dirname, "build"),},module: {
    rules: [{test: /\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          "css-loader",
          {
            loader: "postcss-loader".options: {
              postcssOptions: {
                ident: "postcss"./ / postcss plug-in
                plugins: [require("postcss-preset-env"],},},},],},plugins: [
    new HtmlWebpackPlugin({
      template: "./index.html",}).new MiniCssExtractPlugin({
      filename: "css/build.css",}).new OptimizeCssAssetsWebpackPlugin(),
  ],
  mode: "development"};module.exports = config;

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Compress JS and HTML

To compress the JS code, just change the development mode to production environment.
HTML compression

plugins: [
    new HtmlWebpackPlugin({
      template: "./index.html"./ / HTML compression
      minify: {
        // Remove whitespace
        collapseWhitespace: true.// Remove comments
        removeComments: true,}})],Copy the code

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Webpack learning records

Introduction to WebPack

1. Webpack profile

2. Five core concepts of Webpack

2.1 Entry

2.2 the Output

2.3 Loader

3.3 the Plugins

3.4 Mode

3. Webpack early experience

3.1 Initializing the Project

3.2 Installation Dependencies

conclusion

Configure CSS styles and static resources

4. Package style resources

5. Package HTML resources

6. Pack your photo resources

7. Configuration devserver

8. Extract CSS styles into separate style files

9. CSS compatibility

10. CSS compression

Compress JS and HTML

Webpack learning records

Introduction to WebPack

1. Webpack profile

2. Five core concepts of Webpack

2.1 Entry

2.2 the Output

2.3 Loader

3.3 the Plugins

3.4 Mode

3. Webpack early experience

3.1 Initializing the Project

3.2 Installation Dependencies

conclusion

Configure CSS styles and static resources

4. Package style resources

5. Package HTML resources

6. Pack your photo resources

7. Configuration devserver

8. Extract CSS styles into separate style files

9. CSS compatibility

10. CSS compression

Compress JS and HTML

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