1.create-react-app工作流 #

create-react-app react-project

Creating a new React app in C:\aprepare\react-project.
Installing packages. This might take a couple of minutes.
Installing react, react-dom, and react-scripts with cra-template...
yarn add v1.22.10
info No lockfile found.
[1/4] Resolving packages...
[2/4] Fetching packages...
[3/4] Linking dependencies...
[4/4] Building fresh packages...
success Saved lockfile.
success Saved 881 new dependencies.
Done in 49.71s.
Removing template package using yarnpkg...
yarn remove v1.22.10
[1/2] Removing module cra-template...
[2/2] Regenerating lockfile and installing missing dependencies...
success Uninstalled packages.
Done in 10.19s.
Created git commit.
Success! Created react-project at C:\aprepare\react-project
Inside that directory, you can run several commands:
  yarn start
    Starts the development server.
  yarn build
    Bundles the app into static files for production.    

2.初始化react-scripts2 #

2.1 安装依赖 #

mkdir react-scripts2
cd react-scripts2
npm init -y
yarn add react react-dom
yarn add cross-spawn fs-extra chalk webpack webpack-dev-server babel-loader babel-preset-react-app html-webpack-plugin  open

2.2 package.json #

  "scripts": {
    "build": "node ./bin/react-scripts2 build",
    "start": "node ./bin/react-scripts2 start"
  },
  "bin": {
    "react-scripts2": "./bin/react-scripts2"
  },

2.3 执行命令 #

npm run build
npm run start

3.实现build命令 #

• 1.设置process.env.NODE_ENV = 'production';
• 2.获取webpack配置文件
• 3.清空build目录
• 4.拷贝public目录下的文件到build目录
• 5.创建compiler并调用run方法进行编译

3.1 bin\react-scripts2.js #

bin\react-scripts2.js

const spawn = require('cross-spawn');
const args = process.argv.slice(2);
const script = args[0];
spawn.sync(
    process.execPath,
    [require.resolve('../scripts/' + script)],
    { stdio: 'inherit' }
);

3.2 scripts\build.js #

scripts\build.js

process.env.NODE_ENV = 'production';
const chalk = require('chalk');
const fs = require('fs-extra');
const webpack = require('webpack');
const configFactory = require('../config/webpack.config');
const paths = require('../config/paths');
const config = configFactory('production');

fs.emptyDirSync(paths.appBuild);
copyPublicFolder();
build();

function build() {
    const compiler = webpack(config);
    compiler.run((err, stats) => {
        console.log(err);
        console.log(chalk.green('Compiled successfully.\n'));
    })
}

function copyPublicFolder() {
    fs.copySync(paths.appPublic, paths.appBuild, {
      filter: file => file !== paths.appHtml,
    });
}

3.3 config\paths.js #

config\paths.js

const path = require('path');
const appDirectory = process.cwd();
const resolveApp = relativePath => path.resolve(appDirectory, relativePath);
module.exports = {
    appHtml: resolveApp('public/index.html'),
    appIndexJs:resolveApp('src/index.js'),
    appBuild: resolveApp('build'),
    appPublic: resolveApp('public')
}

3.4 config\webpack.config.js #

config\webpack.config.js

const paths = require('../config/paths');
const HtmlWebpackPlugin = require('html-webpack-plugin');
module.exports = function (webpackEnv) {
    const isEnvDevelopment = webpackEnv === 'development';
    const isEnvProduction = webpackEnv === 'production';
    return {
        mode: isEnvProduction ? 'production' : isEnvDevelopment && 'development',
        output: {
            path: paths.appBuild
        },
        module:{
            rules:[
                {
                    test: /\.(js|jsx|ts|tsx)$/,
                    include: paths.appSrc,
                    loader: require.resolve('babel-loader'),
                    options: {
                      presets: [
                        [
                          require.resolve('babel-preset-react-app')
                        ]
                      ]
                    }
                  },
            ]
        },
        plugins:[
            new HtmlWebpackPlugin({
                inject: true,
                template: paths.appHtml
            })
        ]
    }
}

3.5 src\index.js #

src\index.js

import React from 'react';
import ReactDOM from 'react-dom';
ReactDOM.render(<h1>hello</h1>,document.getElementById('root'));

3.6 public\index.html #

public\index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>react</title>
</head>
<body>
    <div id="root"></div>
</body>
</html>

4.实现start命令 #

4.1 scripts\start.js #

scripts\start.js

process.env.NODE_ENV = 'development';
const configFactory = require('../config/webpack.config');
const createDevServerConfig = require('../config/webpackDevServer.config');
const WebpackDevServer = require('webpack-dev-server');
const DEFAULT_PORT = parseInt(process.env.PORT, 10) || 3000;
const HOST = process.env.HOST || '0.0.0.0';
const config = configFactory('development');
const webpack = require('webpack');
const chalk = require('chalk');
const compiler = createCompiler({ config, webpack });
const serverConfig = createDevServerConfig();
const devServer = new WebpackDevServer(compiler, serverConfig);
devServer.listen(DEFAULT_PORT, HOST, err => {
    if (err) {
        return console.log(err);
    }
    console.log(chalk.cyan('Starting the development server...\n'));
});

function createCompiler({ config, webpack }) {
    let compiler = webpack(config);
    return compiler;
}

4.2 config\webpackDevServer.config.js #

config\webpackDevServer.config.js

module.exports = function () {
    return {
        hot: true
    }
};

5.知识 #

5.1 dotenv #

• 使用dotenv，只需要将程序的环境变量配置写在.env文件中

.env

MONGODB_HOST=localhost
MONGODB_PORT=27017
MONGODB_DB=test
MONGODB_URI=mongodb://${MONGODB_HOST}:${MONGODB_PORT}/${MONGODB_DB}

const dotenvFile = '.env';
require('dotenv-expand')(
    require('dotenv').config({
        path: dotenvFile,
    })
);
console.log(process.env.MONGODB_HOST);
console.log(process.env.MONGODB_PORT);
console.log(process.env.MONGODB_DB);
console.log(process.env.MONGODB_URI);

5.2 NODE_PATH #

• NODE_PATH 就是NODE中用来寻找模块所提供的路径注册环境变量

let fs = require('fs');
let path = require('path');
const appDirectory = fs.realpathSync(process.cwd());
//NODE_PATH folder1;folder2
process.env.NODE_PATH = [
    './a',
    path.resolve(appDirectory, 'b'),
    './c',
].join(path.delimiter);
process.env.NODE_PATH = (process.env.NODE_PATH || '')
  .split(path.delimiter)//windows ; mac :
  .filter(folder => folder && !path.isAbsolute(folder))//不是绝对路径的删除
  .map(folder => path.resolve(appDirectory, folder))//只能是相对目录
  .join(path.delimiter);//再连接在一起
console.log(process.env.NODE_PATH);

5.3 semver-regex #

• 匹配semver版本的正则表达式

const semverRegex = require('semver-regex');
console.log(semverRegex().test('v1.0.0'));
//=> true
console.log(semverRegex().test('1.2.3-alpha.10.beta.0+build.unicorn.rainbow'));
//=> true
console.log(semverRegex().exec('unicorn 1.0.0 rainbow')[0]);
//=> '1.0.0'
console.log('unicorn 1.0.0 and rainbow 2.1.3'.match(semverRegex()));
//=> ['1.0.0', '2.1.3']

const semver = require('semver')
console.log(semver.valid('1.2.3')); // '1.2.3'
console.log(semver.valid('a.b.c')); // null
console.log(semver.clean('  =v1.2.3   ')); // '1.2.3'
console.log(semver.satisfies('1.2.3', '1.x || >=2.5.0 || 5.0.0 - 7.2.3')); // true
console.log(semver.gt('1.2.3', '9.8.7')); // false
console.log(semver.lt('1.2.3', '9.8.7')); // true
console.log(semver.valid(semver.coerce('v2'))); // '2.0.0'
console.log(semver.valid(semver.coerce('42.6.7.9.3-alpha'))); // '42.6.7'

5.4 globby #

• globby是基于 glob，并进一步得到了增强

var globby = require('globby');
(async () => {
    const paths = await globby(['images','photos'],{
      expandDirectories: true
    });
    console.log(paths);
})();

5.5 globalThis #

• globalThis提供统一的机制来访问全局对象
  • Web 浏览器 window
  • Node.js global
  • Web Worker self

// 浏览器环境
console.log(globalThis);    // => Window {...}
// node.js 环境
console.log(globalThis);    // => Object [global] {...}
// web worker 环境
console.log(globalThis);    // => DedicatedWorkerGlobalScope {...}

5.6 bfj #

• bfjBig-Friendly JSON. Asynchronous streaming functions for large JSON data sets.

const bfj = require('bfj');

bfj.read('big.json')
  .then(data => {
    console.log(data);
  })
  .catch(error => {
    console.log(error)
  });

5.7 pnp #

5.7.1 yarn install #

• 1.将依赖包的版本区间解析为某个具体的版本号
• 2.下载对应版本依赖的 tar 包到本地离线镜像
• 3.将依赖从离线镜像解压到本地缓存
• 4.将依赖从缓存拷贝到当前目录的 node_modules 目录

5.7.2 Pnp #

• PnP工作原理是作为把依赖从缓存拷贝到 node_modules 的替代方案

5.7.3 使用 #

5.7.3.1 启用 #

#create-react-app 已经集成了对 PnP 的支持。只需在创建项目时添加 --use-pnp 参数
npx create-react-app react-project --use-pnp 
# 在已有项目中开启 PnP
yarn --pnp
yarn add uuid

5.7.3.2 package.json #

• 只要 installConfig.pnp 的值是一个真值且当前版本的 Yarn 支持，PnP 特性就会被启用

{
  "installConfig": {
    "pnp": true
  }
}

5.7.3.3 uuid.js #

uuid.js

let uuid = require('uuid');
console.log(uuid.v4());

5.7.3.4 运行 #

• 由于在开启了 PnP 的项目中不再有 node_modules 目录，所有的依赖引用都必须由 .pnp.js 中的 resolver 处理
• 因此不论是执行 script 还是用 node 直接执行一个 JS 文件，都必须经由 Yarn 处理

yarn run build
yarn node uuid.js