JS test

test.js

const modern = arr => a.map(i => () => i);

function oldStyle(arr) {
	var res = [];
	var func = function(i) {
		return i;
	};
	for (var i = 0; i <= arr.length; ++i) {
		res.push(func.bind(null, arr[i]));
	}
	return res;
}

let a = [1, 2, 3, 4];

console.log(modern(a)[0]());
console.log(oldStyle(a)[0]());