一. vue源码

我们安装好vue以后， 如何了解vue的的代码结构， 从哪里下手呢？

1.1. vue源码入口

vue的入口是package.json

来分别看看是什么含义

• dependences：

"dependencies": {
"vue": "^2.5.2"
},

这段代码告诉我们vue的版本： 2.5.2

• engines

"engines": {
"node": ">= 6.0.0",
"npm": ">= 3.0.0"
},

指定当前node的版本和npm的版本

• devDependencies
  里面是引入的各种loader

• scripts

"scripts": {
"dev": "webpack-dev-server --inline --progress --config build/webpack.dev.conf.js",
"start": "npm run dev",
"build": "node build/build.js"
},

这就是重点了。 我们npm run build、npm run dev都是执行这里面的命令。 他告诉我们当执行build的时候是在执行那个文件。

1. dev： 读取的配置文件是build/webpack.dev.conf.js
2. build: 读取的配置文件是buld/build.js

1.2.项目文件的结构

先来看看项目的整体目录结构

1.2.1. webpack相关配置

1.2.1.1 webpack.dev.config.js是本地开发环境读取配置文件。

'use strict'
// 定义变量, 生产环境和开发环境区别定义
const utils = require('./utils')
const webpack = require('webpack')
const config = require('../config')
const merge = require('webpack-merge')
const path = require('path')
// 引入公共配置
const baseWebpackConfig = require('./webpack.base.conf')
/**
* 引入插件
*/
// 版权插件
const CopyWebpackPlugin = require('copy-webpack-plugin')
// 打包html到dist文件下, 并自动引入main.js文件
const HtmlWebpackPlugin = require('html-webpack-plugin')
//友好的错误提示插件
const FriendlyErrorsPlugin = require('friendly-errors-webpack-plugin')
const portfinder = require('portfinder')

const HOST = process.env.HOST
const PORT = process.env.PORT && Number(process.env.PORT)

// merge函数: 将两个配置和并. 这里是将基础配置和开发环境的配置进行合并
const devWebpackConfig = merge(baseWebpackConfig, {
module: {
rules: utils.styleLoaders({ sourceMap: config.dev.cssSourceMap, usePostCSS: true })
},
// cheap-module-eval-source-map is faster for development
devtool: config.dev.devtool,

// these devServer options should be customized in /config/index.js
devServer: {
clientLogLevel: 'warning',
historyApiFallback: {
rewrites: [
{ from: /.*/, to: path.posix.join(config.dev.assetsPublicPath, 'index.html') },
],
},
hot: true,
contentBase: false, // since we use CopyWebpackPlugin.
compress: true,
host: HOST || config.dev.host,
port: PORT || config.dev.port,
open: config.dev.autoOpenBrowser,
overlay: config.dev.errorOverlay
? { warnings: false, errors: true }
: false,
publicPath: config.dev.assetsPublicPath,
proxy: config.dev.proxyTable,
quiet: true, // necessary for FriendlyErrorsPlugin
watchOptions: {
poll: config.dev.poll,
}
},
// 开发环境引入的插件
plugins: [
new webpack.DefinePlugin({
'process.env': require('../config/dev.env')
}),
new webpack.HotModuleReplacementPlugin(),
new webpack.NamedModulesPlugin(), // HMR shows correct file names in console on update.
new webpack.NoEmitOnErrorsPlugin(),
// https://github.com/ampedandwired/html-webpack-plugin
new HtmlWebpackPlugin({
filename: 'index.html',
template: 'index.html',
inject: true
}),
// copy custom static assets
new CopyWebpackPlugin([
{
from: path.resolve(__dirname, '../static'),
to: config.dev.assetsSubDirectory,
ignore: ['.*']
}

56c
])
]
})

module.exports = new Promise((resolve, reject) => {
portfinder.basePort = process.env.PORT || config.dev.port
portfinder.getPort((err, port) => {
if (err) {
reject(err)
} else {
// publish the new Port, necessary for e2e tests
process.env.PORT = port
// add port to devServer config
devWebpackConfig.devServer.port = port

// Add FriendlyErrorsPlugin
devWebpackConfig.plugins.push(new FriendlyErrorsPlugin({
compilationSuccessInfo: {
messages: [`Your application is running here: http://${devWebpackConfig.devServer.host}:${port}`],
},
onErrors: config.dev.notifyOnErrors
? utils.createNotifierCallback()
: undefined
}))

resolve(devWebpackConfig)
}
})
})

• webpack.base.conf: 引入了基础项目配置。 公共的配置文件（开发和生产都会使用到的配置文件）都写到这里
• 引入插件： 版权插件、html文件打包插件、有好错题提示插件
• 引入merge包， 将基础配置文件和当前文件合并。

1.2.1.2 build.js是build打包时读取的配置文件

'use strict'
require('./check-versions')()

process.env.NODE_ENV = 'production'

const ora = require('ora')
const rm = requir
ad8
e('rimraf')
const path = require('path')
const chalk = require('chalk')
const webpack = require('webpack')
const config = require('../config')
// 引入了prod配置文件
const webpackConfig = require('./webpack.prod.conf')

...

我们看到build.js引入了webpack.prod.conf配置文件

下面就来看看webpack.prod.conf配置文件都有哪些内容

'use strict'
// 生产环境个性化配置
const path = require('path')
const utils = require('./utils')
// 引入webpack打包工具
const webpack = require('webpack')
const config = require('../config')
// 引入配置合并工具
const merge = require('webpack-merge')
// 引入基础配置文件
const baseWebpackConfig = require('./webpack.base.conf')
// 引入版权配置插件
const CopyWebpackPlugin = require('copy-webpack-plugin')
// 引入html配置合并
const HtmlWebpackPlugin = require('html-webpack-plugin')
// 引入text打包工具
const ExtractTextPlugin = require('extract-text-webpack-plugin')
// 引入css打包工具
const OptimizeCSSPlugin = require('optimize-css-assets-webpack-plugin')
// 引入js压缩工具
const UglifyJsPlugin = require('uglifyjs-webpack-plugin')

// 引入生产环境的配置文件
const env = require('../config/prod.env')

// merge: 将基础配置 + 生产的个性化配置合并
const webpackConfig = merge(baseWebpackConfig, {
module: {
rules: utils.styleLoaders({
sourceMap: config.build.productionSourceMap,
extract: true,
usePostCSS: true
})
},
devtool: config.build.productionSourceMap ? config.build.devtool : false,
output: {
path: config.build.assetsRoot,
filename: utils.assetsPath('js/[name].[chunkhash].js'),
chunkFilename: utils.assetsPath('js/[id].[chunkhash].js')
},
// 生成环境需要使用的插件
plugins: [
// http://vuejs.github.io/vue-loader/en/workflow/production.html
new webpack.DefinePlugin({
'process.env': env
}),
new UglifyJsPlugin({
uglifyOptions: {
compress: {
warnings: false
}
},
sourceMap: config.build.productionSourceMap,
parallel: true
}),
// extract css into its own file
new ExtractTextPlugin({
filename: utils.assetsPath('css/[name].[contenthash].css'),
// Setting the following option to `false` will not extract CSS from codesplit chunks.
// Their CSS will instead be inserted dynamically with style-loader when the codesplit chunk has been loaded by webpack.
// It's currently set to `true` because we are seeing that sourcemaps are included in the codesplit bundle as well when it's `false`,
// increasing file size: https://github.com/vuejs-templates/webpack/issues/1110
allChunks: true,
}),
// Com
564
press extracted CSS. We are using this plugin so that possible
// duplicated CSS from different components can be deduped.
new OptimizeCSSPlugin({
cssProcessorOptions: config.build.productionSourceMap
? { safe: true, map: { inline: false } }
: { safe: true }
}),
// generate dist index.html with correct asset hash for caching.
// you can customize output by editing /index.html
// see https://github.com/ampedandwired/html-webpack-plugin
// html打包插件: 比如:将index.html打包到dist文件夹中.并自动引入bundle.js文件
new HtmlWebpackPlugin({
filename: config.build.index,
template: 'index.html',
inject: true,
minify: {
removeComments: true,
collapseWhitespace: true,
removeAttributeQuotes: true
// more options:
// https://github.com/kangax/html-minifier#options-quick-reference
},
// necessary to consistently work with multiple chunks via CommonsChunkPlugin
chunksSortMode: 'dependency'
}),
// keep module.id stable when vendor modules does not change
new webpack.HashedModuleIdsPlugin(),
// enable scope hoisting
new webpack.optimize.ModuleConcatenationPlugin(),
// split vendor js into its own file
new webpack.optimize.CommonsChunkPlugin({
name: 'vendor',
minChunks (module) {

ad8
// any required modules inside node_modules are extracted to vendor
return (
module.resource &&
/\.js$/.test(module.resource) &&
module.resource.indexOf(
path.join(__dirname, '../node_modules')
) === 0
)
}
}),
// extract webpack runtime and module manifest to its own file in order to
// prevent vendor hash from being updated whenever app bundle is updated
new webpack.optimize.CommonsChunkPlugin({
name: 'manifest',
minChunks: Infinity
}),
// This instance extracts shared chunks from code splitted chunks and bundles them
// in a separate chunk, similar to the vendor chunk
// see: https://webpack.js.org/plugins/commons-chunk-plugin/#extra-async-commons-chunk
new webpack.optimize.CommonsChunkPlugin({
name: 'app',
async: 'vendor-async',
children: true,
minChunks: 3
}),

// copy custom static assets
new CopyWebpackPlugin([
{
from: path.resolve(__dirname, '../static'),
to: config.build.assetsSubDirectory,
ignore: ['.*']
}
])
]
})

if (config.build.productionGzip) {
const CompressionWebpackPlugin = require('compression-webpack-plugin')

webpackConfig.plugins.push(
new CompressionWebpackPlugin({
asset: '[path].gz[query]',
algorithm: 'gzip',
test: new RegExp(
'\\.(' +
config.build.productionGzipExtensions.join('|') +
')$'
),
threshold: 10240,
minRatio: 0.8
})
)
}

if (config.build.bundleAnalyzerReport) {
const BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin
webpackConfig.plugins.push(new BundleAnalyzerPlugin())
}

module.exports = webpackConfig

• 这prod.config.js中引入了webpack.base.conf
• 引入了一些插件： 版权配置插件， html打包插件，text打包工具、css打包压缩工具、js压缩工具。
• 读取了config/prod.env配置文件。
• 使用merge合并基础配置

1.2.2 .babelrc配置文件：ES代码相关转化配置

{
"presets": [
["env", {
"modules": false,
"targets": {
"browsers": ["> 1%", "last 2 versions", "not ie <= 8"]}
}],
"stage-2"
],
"plugins": ["transform-vue-jsx", "transform-runtime"]
}

这是将es6的语法转换成es5. 转换的目标是什么呢

"browsers": ["> 1%", "last 2 versions", "not ie <= 8"]

1. 市场份额大于1%
2. 转换浏览器的最后两个版本
3. ie8以下的版本不转化

1.2.3 .editorconfig文本编辑相关配置

root = true

[*]
charset = utf-8
indent_style = space
indent_size = 2
end_of_line = lf
insert_final_newline = true
trim_trailing_whitespace = true

• charset: 配置文本的字符编码格式
• indent_style: 默认的缩进方式是空格
• indent_size: 缩进空格数是2个
• end_of_line: 尾部处理方式
• insert_final_newline: 尾部自动增加一个单行
• trim_trailing_whitespace: 是否自动格式化空格

1.2.4 .eslintrc.js esLint相关的设置

esLint格式化内容配置, 我们可以启动或者关闭eslint.

1.3. vue访问入口

vue的访问入口是index.html, 当我们执行

npm run dev

的时候， 其实是将文件打包的过程， 和npm run build的区别是， 它是将文件打包到内存。 然后运行在本地服务器。而npm run build是打包到磁盘dist文件夹

1.3.1 访问入口

vue访问的入口是main.js

// The Vue build version to load with the `import` command
// (runtime-only or standalone) has been set in webpack.base.conf with an alias.
import Vue from 'vue'
import App from './App'
import router from './router'

Vue.config.productionTip = false

/* eslint-disable no-new */
new Vue({
el: '#app',
router,
components: { App },
template: '<App/>'
})

• 引入了vue
• 引入了./App.vue， 当前目录的App.vue配置文件
• 当前vue的作用dom元素是id="app"的元素
• 引入了App组件。 App组件，定义在App.vue中
• 使用App组件替代id="app"的元素。

下面来看看App.vue

<template>
<div id="app">
<img src="./assets/logo.png">
<HelloWorld/>
</div>
</template>

<script>
import HelloWorld from './components/HelloWorld'
export default {
name: 'App',
components: {
HelloWorld
}
}
</script>

<style>
#app {
font-family: 'Avenir', Helvetica, Arial, sans-serif;
-webkit-font-smoothing: antialiased;
-moz-osx-font-smoothing: grayscale;
text-align: center;
color: #2c3e50;
margin-top: 60px;
}
</style>

• 首先引入了HelloWorld组件

import HelloWorld from './components/HelloWorld'

• 将组件注册到名为App的组件中
• 在模板中引入HelloWorld组件

然后，我们就看到vue首页的效果了。了解源码入口，方便我们后续代码.