Demonstrates the avoidance of a closure for the trivial task of getting a time difference from invocation using a generator.

ES5.js

var dt = (function () {
	var start = Date.now();

	return function () {
		return Date.now() - start;
	};
})();

// Some time later...

console.log(dt())

ES6.js

var dt = (() => {
	let gen = (function* () {
		let start = Date.now();
	
		while (true) {
			yield Date.now() - start;
		}
	})();
	
	gen.next(); // Start the clock...
	
	return gen;
})();

// Some time later...

console.log(dt.next().value);