JSFiddle - React, Tailwind, and code Playground

JavaScript

var array = [1,2,3];
console.log("pristine array prototype:");
for(var i in array) {
	console.log(i);
}

Array.prototype.duplicates = function() {};

console.log("monkeypatched array prototype:");
for(var i in array) {
	console.log(i);
}