leaky-debounce.js

function leakyDebounce(fn, delay, max = 1) {
	let timer, ctx, args, outstanding = 0, queue = [];

    function done() {
		[ ctx, args ] = queue.shift();
		fn.apply(ctx, args);
		if (queue.length) {
		    timer = setTimeout(done, delay);
        }
    }

  return function(...innerArgs) {
	if (queue.length >= max) { return; }

	queue.push([ this, args ]);
    clearTimeout(timer);
    timer = setTimeout(done, delay);
  };
}