how to allow cross origin request in a node js api code example

Example 1: allow cross origin node

app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
  next();
});

Example 2: cors npm

/* 
Installation
$ npm install cors
*/

// Simple Usage (Enable All CORS Requests)
var express = require("express");
var cors = require("cors");
var app = express();

app.use(cors());

app.get("/products/:id", function (req, res, next) {
   res.json({ msg: "This is CORS-enabled for all origins!" });
});

app.listen(80, function () {
   console.log("CORS-enabled web server listening on port 80");
});