当我自定义文件scss时，laravel混合

Question

当我想要自定义Scss文件时 我把这个命令 npm run dev 但不起作用 看来我这个错误

@ development D:\xammp\htdocs\lasp
cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js

'cross-env' is not recognized as an internal or external command,operable program or batch file.
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! @ development: `cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the @ development script.
npm ERR! This is probably not a problem with npm.

上面可能还有其他日志记录输出。

，我使用laravel 5.4版 npm -v 6.5.0 节点-v v11.9.0