Asynchronous Function Concurrent Executor

concurrent.js

const concurrent = async(limit, fns) => {
	const result = [];
	const runningTasks = [];
	for (const fn of fns) {
		const promise = fn();
		result.push(promise);
		const emptyIndex = runningTasks.length === limit ? await Promise.race(runningTasks) : runningTasks.length;
		const currentIndex = emptyIndex;
		runningTasks[emptyIndex] = promise.then(() => currentIndex);
	}
	return await Promise.all(result);
};

TODO: 각 task의 weight가 1로 한정되지 않고, 사용자가 넣을 수 있게 하기