Await implemented in ES6.

await.es6.js

function await(generatorFunction) {
	let gen = generatorFunction();

	function next(err, result) {
		if (err) {
			gen.throw(err instanceof Error ? err : new Error(err));
		}

		let nextResult = gen.next(result);
		let value = nextResult.value;

		if (nextResult.done) {
			return;
		}

		value.then(
			result => next(null, result),
			e => next(e)
		);
	}

	next();
}

function generateRandomNumber() {
	return new Promise(resolve => setTimeout(() => resolve(Math.random()), 2000));
}

function makeError() {
	return new Promise((r, reject) => reject('Some error'));
}

await(function*() {
	try {
		console.log('Starting random number generator');
		console.log('Random number is', yield generateRandomNumber());
		console.log('Starting another random number generator');
		console.log('Another random number is', yield generateRandomNumber());
		console.log('Throwing error');
		yield makeError();
	} catch (e) {
		console.error('Caught error', e);
	}
});