行数
https://github.com/a8397550/react-source-share/blob/master/default/react-dom-default.js

代码行数 21526行 scheduleUpdateOnFiber

执行 21911 行 renderRoot(root, Sync, true); // 返回了一个这个哦 commitRoot.bind(…)
注意 21654 行 scheduleCallbackForRoot 

  1. var scheduleWork = scheduleUpdateOnFiber;
  2. function scheduleUpdateOnFiber(fiber, expirationTime) {
  3.   checkForNestedUpdates();
  4.   warnAboutInvalidUpdatesOnClassComponentsInDEV(fiber);
  6.   var root = markUpdateTimeFromFiberToRoot(fiber, expirationTime);
  7.   if (root === null) {
  8.     warnAboutUpdateOnUnmountedFiberInDEV(fiber);
  9.     return;
  10.   }
  11.     // NoWork 常量 0
  12.   root.pingTime = NoWork;
  14.   function checkForInterruption(fiberThatReceivedUpdate, updateExpirationTime) {
  15.     // 初始化时 变量 workInProgressRoot = null
  16.     // 常量 enableUserTimingAPI = true
  17.     if (enableUserTimingAPI && workInProgressRoot !== null &&
  18.         // updateExpirationTime = 1073741823
  19.         // 变量 renderExpirationTime = 0
  20.         updateExpirationTime > renderExpirationTime) {
  21.       interruptedBy = fiberThatReceivedUpdate;
  22.     }
  23.   }
  24.   checkForInterruption(fiber, expirationTime);
  25.   // record 记录 [ˈrekɔːd , rɪˈkɔːd]
  26.   // schedule 工作计划 [ˈskedʒuːl]
  27.   function recordScheduleUpdate() {
  28.     // enableUserTimingAPI 常量 true
  29.     if (enableUserTimingAPI) {
  30.       // 变量 初始化时 = false
  31.       if (isCommitting) {
  32.         hasScheduledUpdateInCurrentCommit = true;
  33.       }
  34.       // 初始化时 currentPhase = null
  35.       if (currentPhase !== null &&
  36.           currentPhase !== 'componentWillMount'
  37.           && currentPhase !== 'componentWillReceiveProps') {
  38.         hasScheduledUpdateInCurrentPhase = true;
  39.       }
  40.     }
  41.   }
  42.   recordScheduleUpdate();
  43.   // React-DOM render 源码分析二 介绍过这个方法
  44.   // 初始化时 priorityLevel = 97
  45.   var priorityLevel = getCurrentPriorityLevel();
  46.     // 初始化时 expirationTime === 1073741823 === 1073741823 === Sync 
  47.   // true
  48.   if (expirationTime === Sync) {
  49.     if (
  50.             // 常量 NoContext = 0
  51.       // 初始化时 executionContext = 8 LegacyUnbatchedContext = 8
  52.       // 8 & 8 = 8 下条语句初始化时结果为true
  53.       (executionContext & LegacyUnbatchedContext) !== NoContext &&
  54.       // 初始化 (8 & (16 | 32)) === NoContext 结果为true
  55.       (executionContext & (RenderContext | CommitContext)) === NoContext) {
  56.       // 初始化时，此方法啥也没干
  57.       schedulePendingInteractions(root, expirationTime);
  59.       var callback = renderRoot(root, Sync, true);
  60.       while (callback !== null) {
  61.         callback = callback(true);
  62.       }
  63.     } else {
  64.       scheduleCallbackForRoot(root, ImmediatePriority, Sync);
  65.       if (executionContext === NoContext) {
  67.         flushSyncCallbackQueue();
  68.       }
  69.     }
  70.   } else {
  71.     scheduleCallbackForRoot(root, priorityLevel, expirationTime);
  72.   }
  74.   if ((executionContext & DiscreteEventContext) !== NoContext && (
  75.     // Only updates at user-blocking priority or greater are considered
  76.     // discrete, even inside a discrete event.
  77.     priorityLevel === UserBlockingPriority$2 || priorityLevel === ImmediatePriority)) {
  78.     // This is the result of a discrete event. Track the lowest priority
  79.     // discrete update per root so we can flush them early, if needed.
  80.     if (rootsWithPendingDiscreteUpdates === null) {
  81.       rootsWithPendingDiscreteUpdates = new Map([[root, expirationTime]]);
  82.     } else {
  83.       var lastDiscreteTime = rootsWithPendingDiscreteUpdates.get(root);
  84.       if (lastDiscreteTime === undefined || lastDiscreteTime > expirationTime) {
  85.         rootsWithPendingDiscreteUpdates.set(root, expirationTime);
  86.       }
  87.     }
  88.   }
  89. }
  91. function checkForNestedUpdates() {
  92.   // nestedUpdateCount = 0 , 常量 NESTED_UPDATE_LIMIT = 50
  93.   if (nestedUpdateCount > NESTED_UPDATE_LIMIT) {
  94.     nestedUpdateCount = 0;
  95.     rootWithNestedUpdates = null;
  96.     (function () {
  97.       {
  98.         {
  99.           throw ReactError(Error('Maximum update depth exceeded. This can happen when a component repeatedly calls setState inside componentWillUpdate or componentDidUpdate. React limits the number of nested updates to prevent infinite loops.'));
  100.         }
  101.       }
  102.     })();
  103.   }
  105.   {
  106.     // nestedPassiveUpdateCount = 0, 常量 NESTED_PASSIVE_UPDATE_LIMIT = 50
  107.     if (nestedPassiveUpdateCount > NESTED_PASSIVE_UPDATE_LIMIT) {
  108.       nestedPassiveUpdateCount = 0;
  109.       warning$1(false, 'Maximum update depth exceeded. This can happen when a component ' + "calls setState inside useEffect, but useEffect either doesn't " + 'have a dependency array, or one of the dependencies changes on ' + 'every Render.');
  110.     }
  111.   }
  112. }
  114. function warnAboutInvalidUpdatesOnClassComponentsInDEV(fiber) {
  115.   {    
  116.     // 初始化时，fiber.tag = 3, ClassComponent 常量 1
  117.     if (fiber.tag === ClassComponent) {
  118.       switch (phase) {
  119.         case 'getChildContext':
  120.           if (didWarnAboutUpdateInGetChildContext) {
  121.             return;
  122.           }
  123.           warningWithoutStack$1(false, 'setState(...): Cannot call setState() inside getChildContext()');
  124.           didWarnAboutUpdateInGetChildContext = true;
  125.           break;
  126.         case 'render':
  127.           if (didWarnAboutUpdateInRender) {
  128.             return;
  129.           }
  130.           warningWithoutStack$1(false, 'Cannot update during an existing state transition (such as ' + 'within `Render`). Render methods should be a pure function of ' + 'props and state.');
  131.           didWarnAboutUpdateInRender = true;
  132.           break;
  133.       }
  134.     }
  135.   }
  136. }
  1. function markUpdateTimeFromFiberToRoot(fiber, expirationTime) {
  2.   // 初始化时 
  3.   // expirationTime = 1073741823
  4.   // fiber.expirationTime = 0
  5.   if (fiber.expirationTime < expirationTime) {
  6.     fiber.expirationTime = expirationTime;
  7.   }
  8.   // 初始化 fiber.alternate = null
  9.   var alternate = fiber.alternate;
  10.   if (alternate !== null && alternate.expirationTime < expirationTime) {
  11.     alternate.expirationTime = expirationTime;
  12.   }
  13.   // 初始化时 fiber.return = null
  14.   var node = fiber.return;
  15.   var root = null;
  16.   // 常量 3
  17.   if (node === null && fiber.tag === HostRoot) {
  18.     // fiber.stateNode = FiberRootNode
  19.     root = fiber.stateNode;
  20.   } else {
  21.     while (node !== null) {
  22.       alternate = node.alternate;
  23.       if (node.childExpirationTime < expirationTime) {
  24.         node.childExpirationTime = expirationTime;
  25.         if (alternate !== null && alternate.childExpirationTime < expirationTime) {
  26.           alternate.childExpirationTime = expirationTime;
  27.         }
  28.       } else if (alternate !== null && alternate.childExpirationTime < expirationTime) {
  29.         alternate.childExpirationTime = expirationTime;
  30.       }
  31.       if (node.return === null && node.tag === HostRoot) {
  32.         root = node.stateNode;
  33.         break;
  34.       }
  35.       node = node.return;
  36.     }
  37.   }
  39.   if (root !== null) {
  40.     // 初始化时 root.firstPendingTime = 0;
  41.     // 英first 首个 [fɜːst]
  42.     var firstPendingTime = root.firstPendingTime;
  43.     if (expirationTime > firstPendingTime) {
  44.       root.firstPendingTime = expirationTime;
  45.     }
  46.     // 初始化 root.lastPendingTime = 0;
  47.     var lastPendingTime = root.lastPendingTime;
  48.     // NoWork = 0
  49.     if (lastPendingTime === NoWork || expirationTime < lastPendingTime) {
  50.       root.lastPendingTime = expirationTime;
  51.     }
  52.   }
  54.   return root;
  55. }
  1. function schedulePendingInteractions(root, expirationTime) {
  2.   // root FiberRootNode 
  3.   // expirationTime === 1073741823
  5.   // 常量 enableSchedulerTracing = true
  6.   if (!enableSchedulerTracing) {
  7.     return;
  8.   }
  10.     // var ReactInternals$2 = React.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED;
  11.   // var _ReactInternals$Sched$1 = ReactInternals$2.SchedulerTracing;
  12.   // var __interactionsRef = _ReactInternals$Sched$1.__interactionsRef;
  13.   // 加载react-dom时初始化 ，render前就有值了 __interactionsRef.current: Set(0) {} 
  14.   scheduleInteractions(root, expirationTime, __interactionsRef.current);
  15. }
  17. function scheduleInteractions(root, expirationTime, interactions) {
  18.   // 常量 true
  19.   if (!enableSchedulerTracing) {
  20.     return;
  21.   }
  23.   if (interactions.size > 0) {
  24.     var pendingInteractionMap = root.pendingInteractionMap;
  25.     var pendingInteractions = pendingInteractionMap.get(expirationTime);
  26.     if (pendingInteractions != null) {
  27.       interactions.forEach(function (interaction) {
  28.         if (!pendingInteractions.has(interaction)) {
  29.           // Update the pending async work count for previously unscheduled interaction.
  30.           interaction.__count++;
  31.         }
  33.         pendingInteractions.add(interaction);
  34.       });
  35.     } else {
  36.       pendingInteractionMap.set(expirationTime, new Set(interactions));
  38.       // Update the pending async work count for the current interactions.
  39.       interactions.forEach(function (interaction) {
  40.         interaction.__count++;
  41.       });
  42.     }
  44.     var subscriber = __subscriberRef.current;
  45.     if (subscriber !== null) {
  46.       var threadID = computeThreadID(root, expirationTime);
  47.       subscriber.onWorkScheduled(interactions, threadID);
  48.     }
  49.   }
  50. }