reactjs app change port

JavaScript
//in package.json

"start": "react-scripts start"
t0
//linux
"start": "PORT=3006 react-scripts start"
or 
"start": "export PORT=3006 react-scripts start"
//windows
"start": "set PORT=3006 && react-scripts start"

"start": "react-scripts start"
t0
//linux
"start": "PORT=3006 react-scripts start"
or 
"start": "export PORT=3006 react-scripts start"
//windows
"start": "set PORT=3006 && react-scripts start"
Source

Also in JavaScript: