requestIdleCallback

rIC.js

// cannot force call the callback when it times out though
var requestIdleCallback = window.requestIdleCallback || function(callback, {timeout = Infinity}) {
  let startTime = Date.now();

  return setTimeout(function() {
    // 50 -> duration per frame
    var timeRemaining = Math.max(0, 50 - (Date.now() - startTime));
    callback({
      didTimeout: timeRemaining === 0,
      timeRemaining,
    });
  }, 1);
}