首先显示下我所遇到的问题情况(如下截图所示)

这个是我个人解决问题的思路，希望能帮到你解决

1. 首先将node，npm升级到最新的版本

它将安装的当前稳定版本node

sudo npm cache clean -f sudo npm install -g n sudo n stable

安装最新版npm

npm install -g npm 或者 sudo npm -g install npm@latest

2. 删除node_modules,package-lock.json

   rm -rf node_modules
   rm package-lock.json
   npm cache clear --force

3. 重新安装npde_modules： npm install

   sudo npm cache clear
   sudo npm install --force --no-bin-links

   如图所示：
   

4. 在package.json 干掉三行的 cross-env

   {
   "private": true,
   "scripts": {
       "dev": "npm run development",
       "development": "NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js",
       "watch": "npm run development -- --watch",
       "watch-poll": "npm run watch -- --watch-poll",
       "hot": "NODE_ENV=development node_modules/webpack-dev-server/bin/webpack-dev-server.js --inline --hot --config=node_modules/laravel-mix/setup/webpack.config.js",
       "prod": "npm run production",
       "production": "NODE_ENV=production node_modules/webpack/bin/webpack.js --no-progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js"
   },
   "devDependencies": {
       "axios": "^0.19",
       "bootstrap": "^4.0.0",
       "cross-env": "^6.0.3",
       "jquery": "^3.2",
       "laravel-mix": "^4.0.7",
       "lodash": "^4.17.13",
       "popper.js": "^1.12",
       "resolve-url-loader": "^2.3.1",
       "sass": "^1.15.2",
       "sass-loader": "^7.1.0",
       "vue-template-compiler": "^2.6.10"
   }
   }

5. 最后运行：npm run dev npm run watch-poll 大功告成