当我在npm中使用命令启动my-app进行反应时，我得到的错误以下，我也得到了验证错误以下

Question

当我使用命令在npm中启动my-app进行反应时，我得到了以下错误，也得到了验证以下错误：

  

start : This command cannot be run due to the error: The system cannot find the file specified.
At line:1 char:1
+ start my-app
+ ~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Start-Process], InvalidOperationException
    + FullyQualifiedErrorId : InvalidOperationException,Microsoft.PowerShell.Commands.StartProcessCommand

PS F:\Personal\02. My Project\Class-js> npm install npm@latest -g
npm ERR! code E407
npm ERR! 407 Proxy Authentication Required - GET https://registry.npmjs.org/npm

npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Users\sagar.vandure\AppData\Roaming\npm-cache\_logs\2019-12-28T05_44_22_778Z-debug.log