我正在尝试运行npm run devLaravel Mix，但出现此错误：

> @ dev D:\projects\ptcs
> cross-env NODE_ENV=development webpack --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! @ dev: `cross-env NODE_ENV=development webpack --progress --hide-
modules --config=node_modules/laravel-mix/setup/webpack.config.js`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the @ dev script.

我将node.js更新为6.11.0，将npm更新为5.2.0，但这没有帮助。我在Windows 7上运行Homestead。