Answers for "nodejs has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource"

Access to XMLHttpRequest has been blocked by CORS policy node js

/*
npm i cors
or
 yarn add cors
then in your node app
*/
const cors = require('cors');
const corsOptions ={
    origin:'http://localhost:3000', 
    credentials:true,            //access-control-allow-credentials:true
    optionSuccessStatus:200
}
app.use(cors(corsOptions));

express cors policy no 'access-control-allow-origin'

$ npm install cors