Using Watch Mode

官方文档地址：https://webpack.js.org/guides/development/#using-watch-mode

You can instruct webpack to "watch" all files within your dependency graph for changes.

If one of these files is updated, the code will be recompiled so you don't have to run the full build manually.

译文：您可以指示webpack“监视”依赖关系图中的所有文件以进行更改。如果其中一个文件被更新，代码将被重新编译，这样您就不必手动运行完整的构建。