webpack版本：4.29.6
错误内容如下：
➜ webpack node_modules/.bin/webpack app/main.js public/bundle.js
Hash: 422d13339e0d441f0af9
Version: webpack 4.29.6
Time: 85ms
Built at: 2019/04/12 下午10:52:37
1 asset
Entrypoint main = main.js
[0] multi ./app/main.js public/bundle.js 40 bytes {0} [built]
[1] ./app/main.js 97 bytes {0} [built]
[2] ./app/greeter.js 145 bytes {0} [built]
3/buildin/module.js 497 bytes {0} [built]
WARNING in configuration
The 'mode' option has not been set, webpack will fallback to 'production' for this value. Set 'mode' option to 'development' or 'production' to enable defaults for each environment.
You can also set it to 'none' to disable any default behavior. Learn more: https://webpack.js.org/concepts/mode/
ERROR in multi ./app/main.js public/bundle.js
Module not found: Error: Can't resolve 'public/bundle.js' in '/Users/shan/code/my/something_new/webpack'
@ multi ./app/main.js public/bundle.js main[1]
解决方案：执行命令改为node_modules/.bin/webpack app/main.js --output public/bundle.js
Module not found: Error: Can’t resolve错误处理