How to configure webpack file monitoring

In actual project development, we often need to monitor the project build file, and automatically reconstruct a new output file when the source code of the project changes.
The configuration code is as follows:
webpack.config.js
module.export = {
watch:true,
watchOption:{
ignored:/ node_modules / // Ignore files that do not need to be monitored
aggregationTimeout: 300,
poll: 1000 // The default access is 1000 per second

                     }
                }

                在执行时候的命令  带上参数--watch  如 webpack--watch