// 计算需要渲染的 item 范围letstartIdx=Math.floor(scrollTop/itemHeight);letendIdx=Math.floor((scrollTop+containerHeight)/itemHeight); 首先算第一个 item 的位置 startIdx。 我们用 scrollTop 除以列表项高度 itemHeight,我们就知道 scrollTop 经过了多个 item,将得到的结果向下取整就是可视区域中的第一个...
function validateChildKeys(node, parentType) { if (typeof node !== 'object') { return; } // 检查数组中的item是否有keys if (Array.isArray(node)) { for (var i = 0; i < node.length; i++) { var child = node[i]; if (isValidElement(child)) { validateExplicitKey(child, parent...
You can find other built-in Hooks in the React API reference. You can also write your own Hooks by combining the existing ones. Hooks are more restrictive than regular functions. You can only call Hooks at the top level of your components (or other Hooks). If you want to useState in ...
// 自动捕获GET_INIT_ITEM类型的action,并执行func yield takeEvery(GET_INIT_ITEM, func) } export default mySaga 发送action componentDidMount(){ const action = getInitTodoItemAction() store.dispatch(action) } 4. Redux 怎么实现属性传递,介绍下原理 react-redux 数据传输∶ view-->action-->reducer-...
getStartIndexForOffset:(props:Props<any>,offset:number,instanceProps:InstanceProps):number=>findNearestItem(props,instanceProps,offset) 有了起始数据之后,我们在原先 scrollOffset 的基础上,加上配置的列表高度,就可以得到可见区域底部的高度。程序上,我们从起始位置开始,向下寻找第一个在可见区域之下的行。
findDOMNode 和 refs 都无法用于无状态组件中,原因在前面已经说过。无状 态组件挂载时只是方法调用,没有新建实例。 对于React 组件来说,refs 会指向一个组件类的实例,所以可以调用该类定义的任何方法。 如果需要访问该组件的真实 DOM,可以用 ReactDOM.findDOMNode 来找到 DOM 节点,但我们并 不推荐这样做。因为这...
('vertical'|'horizontal'|null)='vertical';// Layout is an array of objects with the format:// The index into the layout must match the key used on each item component.// If you choose to use custom keys, you can specify that key in the layout// array objects using the `i` prop...
(especially beforereact-dom). Make sure to remove the import before deploying to production, as it carries a large DevTools client with it. If you use Webpack and have control over its configuration, you could alternatively add'react-devtools'as the first item in theentryarray of the ...
Luckily, I’ve been able to find worthy replacements in react-pikaday and react-select. I’ve tested more than 10 libraries, and these two came out as the best. They are dead easy to use, as well: import Pikaday from 'react-pikaday'; import Select from 'react-select'; export default...
components/Book.js create mode 100644 src/components/BookForm.js create mode 100644 src/components/BooksList.js create mode 100644 src/components/EditBook.js create mode 100644 src/components/Header.js create mode 100644 src/context/BooksContext.js create mode 100644 src/hooks/useLocalStorage.js ...