This code was coming up all over the place and I wanted to make it easy to find.

repeatProcess.js

function addFeedsIfNecessary (urlsToCheck, callback) {
	const ctTotalFeeds = urlsToCheck.length;
	var ixNext = 0, ctInFlight = 0, ctDone = 0;
	function startMore () {
		while (true) {
			if (ctInFlight >= config.maxConcurrentFeedChecks) {
				break;
				}
			if (ixNext >= ctTotalFeeds) {
				break;
				}
			const url = urlsToCheck [ixNext++];
			ctInFlight++;
			addFeedIfNecessary (url, function (err) {
				ctInFlight--;
				if (++ctDone >= ctTotalFeeds) {
					callback ();
					}
				else {
					startMore ();
					}
				});
			}
		}
	if (ctTotalFeeds > 0) {
		startMore ();
		}
	else {
		callback ();
		}
	}