如果fetchData函数在组件卸载时被调用,if代码块不会执行是因为isMounted设置为false。 代码语言:javascript 代码运行次数:0 运行 AI代码解释 asyncfunctionfetchData(){constresult=awaitPromise.resolve(['hello','world']);// 👇️ only update state if component is mountedif(isMounted){setState(result);}}...
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 2 3 ...
做项目的过程中,来回切换页面时,一直遇到Can only update a mounted or mounting component这个问题,原因是当离开页面以后,组件已经被卸载,执行setState时无法找到渲染组件。 解决办法特别简单,在离开页面时的周期函数(componentWillUnmount)中: //组件将被卸载componentWillUnmount(){//重写组件的setState方法,直接返回...
如果需要渲染的组件比较庞大,js执行会占据主线程时间较长,会导致页面响应度变差,使得动画、手势交互等事件产生卡顿。 为了解决这个问题,React 提供pureComponent,shouldComponentUpdate,useMemo,useCallback让开发者来操心哪些subtree是需要重新渲染的,哪些是不需要重新渲染的。究其本质,是因为 React 采用 jsx 语法过于灵活,...
= ({ component: Component, ...rest }) => { const [isAuthed,...
Warning: setState(...): Can only update a mounted or mounting component. That warning might appear if there are two components usingtrackWindowScrollat the same time. Notice it's not possible to have a LazyLoadImage/LazyLoadComponent inside another LazyLoadComponent for now. Also, make sure yo...
The reason these are needed is because internally we call ReactDOM.render which starts a new set of lifecycle calls. This set of lifecycle calls are sometimes triggered after the lifecycle of the parent component, so these callbacks provide a hook to know when the frame contents are mounted ...
app.component('MyComponent', { template: `I am a plugin component` }) // 3. 注册全局指令 app.directive('focus', { mounted(el) { el.focus() } }) } } 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16....
This is used because on mount, we’d like the component to check if the HOC is visible. The largest function of our component, _scroll(), grabs the HOC Component’s DOM element with DOM.findDOMNode() and then gets the elements position. This position is compared to the height of the...
memoizedState; if (suspenseState !== null && suspenseState.dehydrated !== null) { invariant( workInProgress.alternate !== null, 'Threw in newly mounted dehydrated component. This is likely a bug in ' + 'React. Please file an issue.', ); resetHydrationState(); } } const flags = ...