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Webpack 5 Series (IV): configuration of Babel
2021-08-26 00:23:47 【Small stars in ceramics】
One 、 Preface
The last one talked about how to Configure a basic development environment . This article will introduce to JS Handling of documents .
Two 、babel-loader
index.js
// Arrow function
const add = (a, b) => a + b;
// Promise object
const promise1 = new Promise((resolve, reject) => {
setTimeout(() => {
resolve(add(1, 2));
}, 1000);
});
const promise2 = new Promise((resolve, reject) => {
setTimeout(() => {
resolve(add(3, 4));
}, 1000);
});
const promise3 = new Promise((resolve, reject) => {
setTimeout(() => {
resolve(add(5, 6));
}, 1000);
});
Promise.all([promise1, promise2, promise3]).then(values => {
console.log(values); // [3, 7, 11]
});
// Example method :Array.prototype.includes()
const arr = [1, 2, 3, 4, 5];
console.log(arr.includes(3)); // true
const root = document.getElementById('root');
root.innerHTML = add(1, 3);
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There are some versions of browsers for JS New syntax ( for example ES6+) Poor support , At this point, you need to convert the new syntax into ES5 Standard grammar , Let the browser recognize them properly , Ensure the stable operation of the program .
To achieve this transformation , What should we do ? use Babel, It will convert the new grammar into the old grammar .
1. Dependent installation
install :
npm install -D babel-loader @babel/core @babel/preset-env
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2. Loader To configure
webpack.config.js
module: {
rules: [
{
test: /\.m?js$/,
exclude: /node_modules/,
use: {
loader: 'babel-loader'
}
}
]
}
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about babel Configuration of , We usually put it in babel.config.json in , Create a new... In the root directory babel.config.json.
3、 ... and 、Babel Configuration of
1. In general babel To configure
babel.config.json
{
"presets": [
["@babel/preset-env", {
"useBuiltIns": "usage", // Introduce on demand corejs Module in
"corejs": 3, // The core js edition
"targets": "> 0.25%, not dead" // Browser support range
}]
]
}
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Also need to download dependencies :
npm i [email protected] --save
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Be careful : Must be configured useBuiltIns, If you don't configure ,babel Will not deal with Promise、Map、Set、Symbol Wait for the global object ;corejs Also configure ,2 The version of can handle global objects , But the instance method does not handle , So here we use 3 Version of .
2. The best babel To configure
If you're writing a library , It's best to add plug-ins —— babel/plugin-transform-runtime, The configuration is as follows :
{
"presets": [
["@babel/preset-env", {
"targets": "> 0.25%, not dead"
}]
],
"plugins": [
// Don't pollute the whole situation , Load at run time
["@babel/plugin-transform-runtime", {
"corejs": 3
}]
]
}
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Also need to download dependencies :
npm install --save-dev @babel/plugin-transform-runtime
npm install --save @babel/runtime
npm install --save @babel/runtime-corejs3
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Four 、 Final remarks
Babel After version update , A lot of content has changed , Official documents are also obscure and difficult to read , Many articles on the Chinese Internet are out of date , Fortunately, I saw a big man's article , That's what makes me right @babel/preset-env and @babel/plugin-transform-runtime Have a basic understanding of . article link At the end of the article , Please read by yourself .
- @babel/preset-env just transforms code with syntax, if we don’t config useBuiltIns.
- @babel/transform-runtime can provide re-use helpers, but don’t polyfill by default.
- Most situation best config: use @babel/preset-env transforms syntax. use @babel/transform-runtime avoid duplicate code, and config corejs: 3 to polyfill.
Reference resources :www.zzuu666.com/articles/9
copyright notice
author[Small stars in ceramics],Please bring the original link to reprint, thank you.
https://en.qdmana.com/2021/08/20210826002344432L.html
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