objectEntries.js

function* objectEntries(obj) {
	let propKeys = Reflect.ownKeys(obj);

	for (let propKey of propKeys) {
		yield [propKey, obj[propKey]];
	}
}

let jane = { first: 'Jane', last: 'Doe' };
for (let [key, value] of objectEntries(jane)) {
	console.log(`${key}: ${value}`);
}