在 Laravel 8 新安装中，mix未被识别为内部或外部命令

I have installed a new Laravel 8 application, and then I ran...

npm install

Afterward, I ran...

npm run dev

我得到以下错误.

"mix"不被识别为内部或外部命令

> @ dev E:\wamp64\www\Laravel8Projects\Laravel_Livewire_JetStream_Projects\jetstream_blog
> npm run development


> @ development E:\wamp64\www\Laravel8Projects\Laravel_Livewire_JetStream_Projects\jetstream_blog
> mix

"mix"不被识别为内部或外部命令, operable
program or batch file. npm ERR! code ELIFECYCLE npm ERR! errno 1 npm
ERR! @ development: `mix` npm ERR! Exit status 1 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 ERR! A complete log of this run can be found in: npm ERR!    
C:\Users\HP\AppData\Roaming\npm-cache\_logs\2021-01-18T17_03_24_944Z-debug.log
npm ERR! code ELIFECYCLE npm ERR! errno 1 npm ERR! @ dev: `npm run
development` npm ERR! Exit status 1 npm ERR! npm ERR! Failed at the @
dev script. npm ERR! This is probably not a problem with npm. There is
likely additional logging output above.

npm ERR! A complete log of this run can be found in: npm ERR!    
C:\Users\HP\AppData\Roaming\npm-cache\_logs\2021-01-18T17_03_24_980Z-debug.log