Find left-most fulfilled promise

left-most.js

function findFirst(promises){
	return when(promises).then(function(promises) {
		return recurseFindFirst(0, [], promises);
	});
}

function recurseFindFirst(i, errors, promises) {
	if(i === promises.length) {
		return when.reject(new AggregateError('All promises rejected', errors));
	}

	return when(promises[i]).catch(function(e) {
		errors.push(e);
		return recurseFindFirst(i+1, errors, promises);
	});
}

function AggregateError(msg, errors) {
	Error.call(this);
	this.errors = errors;
	this.message = msg;
	if(Error.captureStackTrace) {
		Error.captureStackTrace(this, AggregateError);
	}
}

AggregateError.prototype = Object.create(Error.prototype);
AggregateError.prototype.constructor = AggregateError;

var testList = [
	when.reject('a'),
	when.reject('b'),
	when.resolve('c'),
	when.reject('d')
];

findFirst(testList).done(console.log);