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                // 如果不传 callback 回调函数,就会返回一个 Compiler 实例,用于让你去控制启动,而不是像上面那样立即启动
const compiler = webpack(config);

// 调用 以监听模式启动,返回的 watching 用于关闭监听
const watching ={
  // watchOptions
  aggregateTimeout: 300,
},(err, stats)=>{
  // 每次因文件发生变化而重新执行完构建后

// 调用 watching.close 关闭监听 
  // 在监听关闭后