1. gulp 入口文件 gulpfile.js

exports.foo = done => {
  console.log('foo task working');
  done();//任务完成
}
exports.default = done => {
  console.log('default task woking');
  done();
}
传统做法，推荐以上做法
const gulp = require('gulp')
gulp.task('bar',done => {
  console.log('bar working');
  done()
})

2. 介绍series、parallel，前者依次触发，后者并行触发

const { series, parallel} = require('gulp')
const task1 = done =>{
  setTimeout(() => {
    console.log('task1 working')
    done()
  },1000)
}

const task2 = done => {
  setTimeout(() => {
    console.log('task2 working')
    done()
  },1000)
}

const task3 = done => {
  setTimeout(() => {
    console.log('task3 working')
    done()
  },1000)
}
exports.foo = series(task1 , task2 , task3)
exports.bar = parallel(task1, task2, task3)

3.异步回调

exports.callback = done => {
  console.log('callback task--');
  done();
}

exports.callback_error = done => {
  console.log('error');
  done(new Error('task falled'))
}

exports.promise = () => {
  console.log('promise task...');
  // return Promise.resolve();
  return Promise.reject(new Error('task falled...'))
}
const timeout = time => {
  return new Promise(resolve => {
    setTimeout(resolve,time)
  })
}
exports.async = async() => {
  await timeout(1000)
  console.log('async task...');
}

const fs = require('fs')
exports.stream = () => {
  const readStream = fs.createReadStream('package.json')
  const writeStream = fs.createWriteStream('temp.txt')
  readStream.pipe(writeStream)
  return readStream//存在end结束事件
}

4. 构建过程中核心原理

//读取流 》 转换流 》 写入流
const fs = require('fs')
const { Transform } = require('stream')

exports.default = () => {
  //文件读取流
  const read = fs.createReadStream('demo.css')
  //文件写入流
  const write = fs.createWriteStream('demo.min.css')
  //文件转换流
  const transform = new Transform({
    transform: (chunk, ecodeing, callback) => {
      //核心转换过程实现
      //chunk => 读取流中读取到的内容 （Buffer）
      const input = chunk.toString();
      const output = input.replace(/\s+/g,'').replace(/\/\*.+?\*\//g,'')
      callback(null,output)
    }
  })
  //把读取出来的文件流写入文件流
  read
  .pipe(transform)//转换
  .pipe(write)//转入
  return read
}

5.文件操作API

const {src, dest} = require('gulp')
//安装插件 gulp-clean-css
//安装插件 gulp-rename
const cleancss = require('gulp-clean-css')
const rename = require('gulp-rename')
exports.default = () => {
  return src('src/*.css')
    .pipe(cleancss())
    .pipe(rename({extname: '.min.css'}))
    .pipe(dest('dist'))
}

6. 自动化构建案例

const { src, dest, parallel, series, watch } = require('gulp')
//建立temp，防止边读取边写入造成文件无法生成问题
//区别开发时build和上线之前构建，建立个临时目录temp，最终上线用dist
const del = require('del')
// yarn add browser-sync --dev
const browserSync = require('browser-sync')

const loadPlugins = require('gulp-load-plugins')
//自动加载插件 yarn add gulp-load-plugins --dev
const plugins = loadPlugins()
//创建开发服务器
const bs = browserSync.create()

const data = {
  menus: [
    {
      name: 'Home',
      icon: 'aperture',
      link: 'index.html'
    },
    {
      name: 'Features',
      link: 'features.html'
    },
    {
      name: 'About',
      link: 'about.html'
    },
    {
      name: 'Contact',
      link: '#',
      children: [
        {
          name: 'Twitter',
          link: 'https://twitter.com/w_zce'
        },
        {
          name: 'About',
          link: 'https://weibo.com/zceme'
        },
        {
          name: 'divider'
        },
        {
          name: 'About',
          link: 'https://github.com/zce'
        }
      ]
    }
  ],
  pkg: require('./package.json'),
  date: new Date()
}

const clean = () => {
  //安装 yarn add del --dev
  return del(['dist', 'temp'])
}

const style = () => {
  //安装 yarn add gulp-sass --dev
  return src('src/assets/styles/*.scss', { base: 'src' })
    .pipe(plugins.sass({ outputStyle: 'expanded' }))
    .pipe(dest('temp'))
    .pipe(bs.reload({ stream: true }))//以流的形式推到浏览器
}

const script = () => {
  //安装 yarn add gulp-babel --dev
  // yarn add @babel/core @babel/preset-env --dev
  return src('src/assets/scripts/*.js', { base: 'src' })
    .pipe(plugins.babel({ presets: ['@babel/preset-env'] }))
    .pipe(dest('temp'))
    .pipe(bs.reload({ stream: true }))
}

const page = () => {
  return src('src/*.html', { base: 'src' })
    .pipe(plugins.swig({ data, defaults: { cache: false } })) // 防止模板缓存导致页面不能及时更新
    .pipe(dest('temp'))
    .pipe(bs.reload({ stream: true }))
}

const image = () => {
  //yarn add gulp-imagemin --dev
  return src('src/assets/images/**', { base: 'src' })
    .pipe(plugins.imagemin())
    .pipe(dest('dist'))
}

const font = () => {
  return src('src/assets/fonts/**', { base: 'src' })
    .pipe(plugins.imagemin())
    .pipe(dest('dist'))
}

const extra = () => {
  //拷贝
  return src('public/**', { base: 'public' })
    .pipe(dest('dist'))
}
//初始化服务器配置
const serve = () => {
  //监听源文件变化
  watch('src/assets/styles/*.scss', style)
  watch('src/assets/scripts/*.js', script)
  watch('src/*.html', page)
  // watch('src/assets/images/**', image)
  // watch('src/assets/fonts/**', font)
  // watch('public/**', extra)
  //减少构建次数
  watch([
    'src/assets/images/**',
    'src/assets/fonts/**',
    'public/**'
  ], bs.reload)

  bs.init({
    notify: false,//服务器提示
    port: 2080,//端口
    // open: false,//默认开启浏览器
    // files: 'dist/**',//指定dist文件发生改变及时热部署
    server: {
      baseDir: ['temp', 'src', 'public'],//设置根目录
      routes: {//特殊路由，优先basedir从这里寻找文件
        '/node_modules': 'node_modules'     }
    }
  })
}

const useref = () => {
  //yarn add gulp-useref --dev
  return src('temp/*.html', { base: 'temp' })
    .pipe(plugins.useref({ searchPath: ['temp', '.'] }))
    // html js css
    //yarn add gulp-htmlmin gulp-uglify gulp-clean-css --dev
    //yarn add gulp-if --dev
    .pipe(plugins.if(/\.js$/, plugins.uglify()))
    .pipe(plugins.if(/\.css$/, plugins.cleanCss()))
    .pipe(plugins.if(/\.html$/, plugins.htmlmin({
      collapseWhitespace: true,//删除空格
      minifyCSS: true,//压缩行内样式
      minifyJS: true//压缩行内js
    })))
    .pipe(dest('dist'))
}

const compile = parallel(style, script, page)

// 上线之前执行的任务
const build =  series(
  clean,
  parallel(
    series(compile, useref),//useref依赖compile
    image,
    font,
    extra
  )
)
//开发时执行
const develop = series(compile, serve)

module.exports = {
  clean,
  build,
  develop
}

7.封装工作流