手写 plugin

class firstPlugin {
  constructor(options) {
    this.options = options
  }
  apply(compiler) {
    compiler.plugin('emit', (compilation, callback) => {
      let str = ''
      for (let filename in compilation.assets) {
        str += `文件:${filename}  大小${compilation.assets[filename]['size']()}\n`
      }
      // 通过compilation.assets可以获取打包后静态资源信息，同样也可以写入资源
      compilation.assets['fileSize.md'] = {
        source: function () {
          return str
        },
        size: function () {
          return str.length
        }
      }
      callback()
    })
  }
}
module.exports = firstPlugin

使用

const path = require('path')
const firstPlugin = require('webpack-firstPlugin.js')
module.exports = {
  // 省略其他代码
  plugins: [new firstPlugin()]
}