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Update usestate.md #67

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6 changes: 3 additions & 3 deletions docs/hooks/usestate.md
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Expand Up @@ -253,11 +253,11 @@ if (fiber.lanes === NoLanes && (alternate === null || alternate.lanes === NoLane

`fiber.lanes === NoLanes`意味着`fiber`上不存在`update`。

我们已经知道，通过`update`计算`state`发生在`申明阶段`，这是因为该`hook`上可能存在多个不同`优先级`的`update`，最终`state`的值由多个`update`共同决定。
我们已经知道，通过`update`计算`state`发生在`声明阶段`，这是因为该`hook`上可能存在多个不同`优先级`的`update`，最终`state`的值由多个`update`共同决定。

但是当`fiber`上不存在`update`，则`调用阶段`创建的`update`为该`hook`上第一个`update`，在`申明阶段`计算`state`时也只依赖于该`update`，完全不需要进入`申明阶段`再计算`state`。
但是当`fiber`上不存在`update`，则`调用阶段`创建的`update`为该`hook`上第一个`update`，在`声明阶段`计算`state`时也只依赖于该`update`，完全不需要进入`声明阶段`再计算`state`。

这样做的好处是：如果计算出的`state`与该`hook`之前保存的`state`一致，那么完全不需要开启一次调度。即使计算出的`state`与该`hook`之前保存的`state`不一致，在`申明阶段`也可以直接使用`调用阶段`已经计算出的`state`。
这样做的好处是：如果计算出的`state`与该`hook`之前保存的`state`一致，那么完全不需要开启一次调度。即使计算出的`state`与该`hook`之前保存的`state`不一致，在`声明阶段`也可以直接使用`调用阶段`已经计算出的`state`。

> 你可以在[这里](https://github.com/acdlite/react/blob/1fb18e22ae66fdb1dc127347e169e73948778e5a/packages/react-reconciler/src/ReactFiberHooks.new.js#L1727)看到这段提前计算`state`的逻辑

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