我想在我的 laravel 项目中执行“npm run watch”，但它不起作用。有错误信息
@watch /Applications/MAMP/htdocs/test-tech/laravel5 npm run development -- --watch
@ development /Applications/MAMP/htdocs/test-tech/laravel5 cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack .config.js "--watch"
sh: cross-env: command not found npm ERR！文件 sh npm 错误！代码 ELIFECYCLE npm 错误！errno ENOENT npm 错误！系统调用产生 npm 错误！//@开发：cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js "--watch"
npm ERR！产生 ENOENT npm 错误！npm 错误！@开发脚本失败。npm 错误！这可能不是 npm 的问题。上面可能有额外的日志输出。npm WARN 本地 package.json 存在，但缺少 node_modules，你的意思是要安装吗？
npm 错误！可以在以下位置找到此运行的完整日志：npm ERR！/Users/xxx/.npm/_logs/2019-03-29T11_19_55_390Z-debug.log npm 错误！代码 ELIFECYCLE npm 错误！errno 1 npm 错误！//@手表：npm run development -- --watch
npm ERR！退出状态 1 npm ERR！npm 错误！@watch 脚本失败。npm 错误！这可能不是 npm 的问题。上面可能有额外的日志输出。npm WARN 本地 package.json 存在，但缺少 node_modules，你的意思是要安装吗？
npm 错误！可以在以下位置找到此运行的完整日志：npm ERR！/Users/xxx/.npm/_logs/2019-03-29T11_19_55_422Z-debug.log
和调试文件
0 info it worked if it ends with ok
1 verbose cli [ '/usr/local/bin/node', '/usr/local/bin/npm', 'run', 'watch' ]
2 info using npm@5.6.0
3 info using node@v8.11.3
4 verbose run-script [ 'prewatch', 'watch', 'postwatch' ]
5 info lifecycle @~prewatch: @
6 info lifecycle @~watch: @
7 verbose lifecycle @~watch: unsafe-perm in lifecycle true
8 verbose lifecycle @~watch: PATH: /usr/local/lib/node_modules/npm/node_modules/npm-lifecycle/node-gyp-bin:/Applications/MAMP/htdocs/test-tech/laravel5/node_modules/.bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
9 verbose lifecycle @~watch: CWD: /Applications/MAMP/htdocs/test-tech/laravel5
10 silly lifecycle @~watch: Args: [ '-c', 'npm run development -- --watch' ]
11 silly lifecycle @~watch: Returned: code: 1 signal: null
12 info lifecycle @~watch: Failed to exec watch script
13 verbose stack Error: @ watch: `npm run development -- --watch`
13 verbose stack Exit status 1
13 verbose stack at EventEmitter.<anonymous> (/usr/local/lib/node_modules/npm/node_modules/npm-lifecycle/index.js:285:16)
13 verbose stack at emitTwo (events.js:126:13)
13 verbose stack at EventEmitter.emit (events.js:214:7)
13 verbose stack at ChildProcess.<anonymous> (/usr/local/lib/node_modules/npm/node_modules/npm-lifecycle/lib/spawn.js:55:14)
13 verbose stack at emitTwo (events.js:126:13)
13 verbose stack at ChildProcess.emit (events.js:214:7)
13 verbose stack at maybeClose (internal/child_process.js:925:16)
13 verbose stack at Process.ChildProcess._handle.onexit (internal/child_process.js:209:5)
14 verbose pkgid @
15 verbose cwd /Applications/MAMP/htdocs/test-tech/laravel5
16 verbose Darwin 18.2.0
17 verbose argv "/usr/local/bin/node" "/usr/local/bin/npm" "run" "watch"
18 verbose node v8.11.3
19 verbose npm v5.6.0
20 error code ELIFECYCLE
21 error errno 1
22 error @ watch: `npm run development -- --watch`
22 error Exit status 1
23 error Failed at the @ watch script.
23 error This is probably not a problem with npm. There is likely additional logging output above.
24 verbose exit [ 1, true ]
我用谷歌搜索并尝试了一些解决方案，但仍然无法正常工作。如何解决？
谢谢