Добавил clean-webpack-plugin

build/webpack.base.config.js

@@ -3,11 +3,11 @@ const webpack = require("webpack");
 const VueLoaderPlugin = require('vue-loader/lib/plugin');
 
 module.exports = {
-    entry: [path.resolve(__dirname, "../client/main.js")],
+    entry: [path.resolve(__dirname, '../client/main.js')],
     output: {
-        path: path.resolve(__dirname, "../server/public/app"),
+        path: path.resolve(__dirname, '../server/public/app'),
-        publicPath: "/app/",
+        publicPath: '/app/',
-        filename: "bundle.js"
+        filename: 'bundle.js'
     },
 
     module: {

build/webpack.prod.config.js

@@ -4,6 +4,7 @@ const webpack = require("webpack");
 const merge = require("webpack-merge");
 const baseWpConfig = require("./webpack.base.config");
 const MiniCssExtractPlugin = require("mini-css-extract-plugin");
+const CleanWebpackPlugin = require('clean-webpack-plugin');
 
 module.exports = merge(baseWpConfig, {
     mode: 'production',
@@ -23,6 +24,7 @@ module.exports = merge(baseWpConfig, {
         ]
     },
     plugins: [
+        new CleanWebpackPlugin([`${baseWpConfig.output.path}/*.*`], {root: path.resolve(__dirname, '..')}),
         new MiniCssExtractPlugin({
             filename: "[name].css"
         })

package-lock.json

@@ -1879,6 +1879,15 @@
         }
       }
     },
+    "clean-webpack-plugin": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/clean-webpack-plugin/-/clean-webpack-plugin-1.0.0.tgz",
+      "integrity": "sha512-+f96f52UIET4tOFBbCqezx7KH+w7lz/p4fA1FEjf0hC6ugxqwZedBtENzekN2FnmoTF/bn1LrlkvebOsDZuXKw==",
+      "dev": true,
+      "requires": {
+        "rimraf": "^2.6.1"
+      }
+    },
     "cli-cursor": {
       "version": "2.1.0",
       "resolved": "https://registry.npmjs.org/cli-cursor/-/cli-cursor-2.1.0.tgz",

package.json

@@ -24,6 +24,7 @@
     "babel-plugin-transform-class-properties": "^6.24.1",
     "babel-plugin-transform-decorators-legacy": "^1.3.5",
     "babel-preset-env": "^1.3.2",
+    "clean-webpack-plugin": "^1.0.0",
     "css-loader": "^1.0.0",
     "element-theme-chalk": "^2.4.11",
     "eslint": "^5.11.1",