Function pop

lib/assets/react-source/development/react.js:3050–3065

(heap)

	  return first === undefined ? null : first;
	}
	function pop(heap) {
	  var first = heap[0];

	  if (first !== undefined) {
	    var last = heap.pop();

	    if (last !== first) {
	      heap[0] = last;
	      siftDown(heap, last, 0);
	    }

	    return first;
	  } else {
	    return null;
	  }
	}

	function siftUp(heap, node, i) {
	  var index = i;