Does it feel like when you call this.setState or React.useState, the changes feel like it’s a step behind? Let’s dive into why this.setState and React.useStatedo not update immediately. The answer: They’re just queues React this.setState, and useState does not make changes directly ...
在React中,setState是一个用于更新组件状态的方法。当调用setState时,React会将新的状态合并到当前状态中,并触发组件的重新渲染。 然而,有时候调用setState并不会触发组件的更新,这可能是由于以下几个原因: 状态没有发生变化:如果新的状态与当前状态相同,React会认为没有必要重新渲染组件,因此不会触发更新。 异步更新...
Warning:setState(...):Canonly update a mounted or mounting component.Thisusually means you calledsetState()on an unmounted component.Thisisa no-op.Pleasecheck the codeforthe xxx component. 报这个错误,实际的原因是因为在组件挂载(mounted)之后进行了异步操作,比如ajax请求或者设置了定时器等,而你在call...
1 2 Warning:setState(...): Can only update a mounted or mounting component. This usually means you called setState() on an unmounted component.This is a no-op. Please check the codeforthe xxx component. 通常是因为组件并没有装载上便开始执行setState({}),这时候,我们可以在组件中写入: 1 ...
enqueueSetState: function (publicInstance, partialState) { // 先获取ReactComponent组件对象 var internalInstance = getInternalInstanceReadyForUpdate(publicInstance, 'setState'); if (!internalInstance) { return; } // 如果_pendingStateQueue为空,则创建它。可以发现队列是数组形式实现的 ...
this.setState((state, props) => { return { number: Math.ceil(Math.random() * 3) } }) }; // 两次生成的随机数可能相同,如果相同就没必要重新渲染 // 将要更新UI的时候会执行这个钩子函数 shouldComponentUpdate(nextProps, nextState, nextContext) { ...
解释:这句的话的意思很明显就是告诉你: React的 setState是"异步"的,React在没有重新渲染之前对state的做了一些处理以达到最佳的性能 setState() does not always immediately update the component. It may batch or defer the update until later. This makes reading this.state right ...
简介:react中使用shouldComponentUpdate生命周期函数调用setState引起的无限循环的错误 场景: 在React组件中,当在 componentWillUpdate 或 componentDidUpdate 生命周期方法中调用 setState 时,会触发无限循环,导致超过最大更新深度。 错误原因 在React组件中 ,我们使用componentWillUpdate 或 componentDidUpdate生命周期方法中...
However, when we click it, we get an error. We’ll get something like “this.setState is not a function” or “cannot read property ‘setState’ of undefined”. In either case, an error is thrown and our code stops working.
setState()does not always immediately update the component. It may batch or defer the update until later. This makes readingthis.stateright after callingsetState()a potential pitfall. Instead, usecomponentDidUpdateor asetStatecallback (setState(updater, callback)), either of which are guaranteed...