webpack4   自动清除打包目录

需要使用clean-webpack-plugin插件

const {CleanWebpackPlugin} = require('clean-webpack-plugin');
module.exports = {
	plugins: [
    	new CleanWebpackPlugin()
 	}
}

webpack5   自动清除打包目录

module.exports = {
	output: {
		clean: true
	}
}