Function startTransition

lib/assets/react-source/development/react.js:19217–19233

(setPending, config, callback)

	}

	function startTransition(setPending, config, callback) {
	  var priorityLevel = getCurrentPriorityLevel();
	  runWithPriority$1(priorityLevel < UserBlockingPriority$1 ? UserBlockingPriority$1 : priorityLevel, function () {
	    setPending(true);
	  });
	  runWithPriority$1(priorityLevel > NormalPriority ? NormalPriority : priorityLevel, function () {
	    var previousConfig = ReactCurrentBatchConfig$1.suspense;
	    ReactCurrentBatchConfig$1.suspense = config === undefined ? null : config;

	    try {
	      setPending(false);
	      callback();
	    } finally {
	      ReactCurrentBatchConfig$1.suspense = previousConfig;
	    }
	  });
	}

	function mountTransition(config) {
	  var _mountState2 = mountState(false),