This time I will show you how to hot replace the webpack module, and what are the precautions for hot replacement of the webpack module. The following is a practical case, let's take a look.
The full name is Hot Module Replacement (HMR), which can be understood as hot module replacement or module hot replacement. It has the same meaning as hot swap in .net, which is to update the program module during operation. This function is mainly used in the development process and does not help in the production environment (this is different from .net hot swap). The effect is a refresh-free update of the interface. HMR is based on WDS, and style-loader can use it to update styles without refreshing. But for theconst path = require('path'); const HtmlWebpackPlugin = require('html-webpack-plugin'); const webpack = require('webpack'); const PATHS = { app: path.join(dirname, 'app'), build: path.join(dirname, 'build'), }; const commonConfig={ entry: { app: PATHS.app, }, output: { path: PATHS.build, filename: '[name].js', }, plugins: [ new HtmlWebpackPlugin({ title: 'Webpack demo', }), ], } function developmentConfig(){ const config ={ devServer:{ //使能历史记录api historyApiFallback:true, hotOnly:true,//关闭热替换 注释掉这行就行 stats:'errors-only', host:process.env.Host, port:process.env.PORT, overlay:{ errors:true, warnings:true, } }, plugins: [ new webpack.HotModuleReplacementPlugin(), ], }; return Object.assign( {}, commonConfig, config, { plugins: commonConfig.plugins.concat(config.plugins), } ); } module.exports = function(env){ console.log("env",env); if(env=='development'){ return developmentConfig(); } return commonConfig; };This webpack.config.js creates two configurations, one is commonConfig and the other is developmentConfig. The two are distinguished by the env parameter, but where does this env parameter come from? Let’s take a look at a section of the previous package.json:
plugins: [ new webpack.HotModuleReplacementPlugin(), new webpack.NamedModulesPlugin(), ],Start it again at this time.
import component from './component'; let demoComponent=component(); document.body.appendChild(demoComponent); //HMR 接口 if(module.hot){ module.hot.accept('./component',()=>{ const nextComponent=component(); document.body.replaceChild(nextComponent,demoComponent); demoComponent=nextComponent; }) }and modify component.js:
export default function () { var element = document.createElement('h1'); element.innerHTML = 'Hello webpack'; return element; }
webpackHotUpdate(0,{ /***/ "./app/component.js": /***/ (function(module, webpack_exports, webpack_require) { "use strict"; Object.defineProperty(webpack_exports, "esModule", { value: true }); /* harmony default export */ webpack_exports["default"] = function () { var element = document.createElement('h1'); element.innerHTML = 'Hello web '; element.className='box'; return element; }; /***/ }) })Update the corresponding module through webpackHotUpdate. 0 represents the id of the module, and "./app/component.js" represents the name corresponding to the module. The structure is webpack(id,{key:function(){}}). There is a bracket outside the function, I don’t know what it does. The definition of webpackHotUpdate is as follows:
this["webpackHotUpdate"] = function webpackHotUpdateCallback(chunkId, moreModules) { // eslint-disable-line no-unused-vars hotAddUpdateChunk(chunkId, moreModules); if(parentHotUpdateCallback) parentHotUpdateCallback(chunkId, moreModules); } ;Summary: From a structural point of view, one is the id and the other is the corresponding modified module. But it is the hotApply method that actually performs the update. The whole mechanism of hot update is still a bit complicated, and the effect is like MVVM binding. Those who are interested can study it in depth. It is not recommended to use HMR in production, as it will make the overall file larger and not helpful for generation. In the next section, we will talk about style loading. style-loader uses HMR. But for the js module, you have to write additional code, which is a bit unpleasant. I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website! Recommended reading:
How to build a vue2.0 boostrap project
How to use vue to set proxyTable parameters across domains
Angular entry component and declarative component case comparison
The above is the detailed content of How to hot replace webpack modules. For more information, please follow other related articles on the PHP Chinese website!

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