title: Npm run watch doesn't work with laravel : sh: cross-env: command not found
body: <p>I want to execute "npm run watch" in my laravel project but it doesn't work.
  There is the error message</p>
  
  <blockquote>
    <p>@ watch /Applications/MAMP/htdocs/test-tech/laravel5
    npm run development -- --watch</p>
    
    <p>@ 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"</p>
  </blockquote>
  
  <p>sh: cross-env: command not found
  npm ERR! file sh
  npm ERR! code ELIFECYCLE
  npm ERR! errno ENOENT
  npm ERR! syscall spawn
  npm ERR! @ development: <code>cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js "--watch"</code>
  npm ERR! spawn ENOENT
  npm ERR!
  npm ERR! Failed at the @ development script.
  npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
  npm WARN Local package.json exists, but node_modules missing, did you mean to install?</p>
  
  <p>npm ERR! A complete log of this run can be found in:
  npm ERR!     /Users/xxx/.npm/_logs/2019-03-29T11_19_55_390Z-debug.log
  npm ERR! code ELIFECYCLE
  npm ERR! errno 1
  npm ERR! @ watch: <code>npm run development -- --watch</code>
  npm ERR! Exit status 1
  npm ERR!
  npm ERR! Failed at the @ watch script.
  npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
  npm WARN Local package.json exists, but node_modules missing, did you mean to install?</p>
  
  <p>npm ERR! A complete log of this run can be found in:
  npm ERR!     /Users/xxx/.npm/_logs/2019-03-29T11_19_55_422Z-debug.log</p>
  
  <p>And the debug file</p>
  
  <pre><code>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.&lt;anonymous&gt; (/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.&lt;anonymous&gt; (/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 ]
  
  </code></pre>
  
  <p>I googled it and tried some solutions but it still doesn't work.
  How to resolve it ?</p>
  
  <p>Thanks</p>