JSFiddle - React, Tailwind, and code Playground

JavaScript

var map;

map = new Map();

for(var i=0;i<10;i++) {
	var obj = {foo: "bar"};
  if(map.has(obj)) {
    	console.log("old key ");
			map.set(obj, "foobar "+i);  	
  } else {
  	console.log("new key ");
  				map.set(obj, "new foobar "+i);  	
  }
}