端口被占用的解决办法

events.js:187
      throw er; // Unhandled 'error' event
      ^

Error: listen EADDRINUSE: address already in use 127.0.0.1:3000
    at Server.setupListenHandle [as _listen2] (net.js:1298:14)
    at listenInCluster (net.js:1346:12)
    at GetAddrInfoReqWrap.doListen [as callback] (net.js:1485:7)
    at GetAddrInfoReqWrap.onlookup [as oncomplete] (dns.js:65:10)
Emitted 'error' event on Server instance at:
    at emitErrorNT (net.js:1325:8)
    at processTicksAndRejections (internal/process/task_queues.js:80:21) {
  code: 'EADDRINUSE',
  errno: 'EADDRINUSE',
  syscall: 'listen',
  address: '127.0.0.1',
  port: 3000
}
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! [email protected] dev: `webpack-dev-server --open --port 3000 --hot`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the [email protected] 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\ASUS\AppData\Roaming\npm-cache\_logs\2020-02-18T02_25_46_034Z-debug.log

解决办法：

1.“运行”中输入 cmd

2.在命令行中输入netstat -ano，得到端口号对应的PID并记下。

3.杀掉进程的命令：taskkill /pid 4 /f 其中 /f 表示强制关闭该进程。4代表PID号