how to stop a app using a port in react js code example

Example 1: how to close port 3000 running

### For Linux/Mac OS search (sudo) run this in the terminal:
$ lsof -i tcp:3000
$ kill -9 PID

### On Windows:
netstat -ano | findstr :3000
tskill typeyourPIDhere 

### change tskill for taskkill in git bash

Example 2: npm port already in use

$ lsof -i tcp:3000
$ kill -9 PID