在ReactJs中使用map函数时出现错误"Cannot read property 'map' of undefined",通常是因为在使用map函数之前,没有正确初始化或者传递数据给要被映射的数组。下面是一些可能导致出现这个错误的常见原因和解决方法: 数据未正确初始化:检查数据是否被正确地初始化。确保数据是一个数组,而...
当你在React应用中遇到“Cannot read properties of undefined (reading 'map')”这个错误时,通常是因为你尝试在一个未定义的变量上调用map方法。为了解决这个问题,可以按照以下步骤进行排查和修复: 确认错误位置和上下文: 查看错误堆栈信息,确定是哪一行代码抛出了这个错误。 分析该行代码所在的组件和渲染逻辑。 检查...
看清楚错误提示了吗 Cannot read property 'map' of undefined 是你调用 map 的对象是 undefined,而不是 map 是 undefined 组件初始化的时候的 state 是这样的 { data: [] } 然后你给 ContentList 的listData 属性的值是 this.state.data.listData,这个时候 ajax 还没有返回数据,listData 肯定是 undefined ...
import { ADD_TODO, VisibilityFilters, SET_VISIBILITY_FILTER, } from './actions' import { combineReducers } from 'redux' const { SHOW_ALL } = VisibilityFilters /* let [foo, [[bar], baz]] = [1, [[2], 3]]; foo // 1 bar // 2 baz // 3 let [ , , third] = ["foo", "b...
TypeError: Cannot read properties of undefined (reading 'setExtraStackFrame') 起因: React在渲染某些组件时会出现这个bug导致白屏, 排查经过: 网上查了一下原因,是React组件在map的时候没有加key导致的,加了key后确实就可以了 仔细排查了下原因, 是因为在开发环境下,用了生产环境的React和ReactDOM,并且还没...
userInfo.create_date 这个判断条件，会报cannot read the property split of undefined的错误,为什么插值...
I'm sure this is just me, as I'm still pretty new to React, but I cannot get this working. No matter what I do, I'm seeing "Uncaught TypeError: Cannot read property '__reactAutoBindMap' of undefined" and it is often accompanied by "Warni...
React:TypeError: Cannot read properties of undefined (reading 'map') 解决方案 js中?问号代表可选项 可选链式操作符 参考链接 https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing_operator
I have the following two files and when I put the on any page I get an error: Uncaught TypeError: Cannot read property 'map' of undefined - any ideas? CountryContainer.jsx: import {composeWithTracker} from 'react-komposer' import CountryList from 'common/client/components/list/CountryList....
Cannot read property 'map' of undefined 报错:Cannot read property 'map' of undefine <ul className={styles.resul}>{this.state.isfalsepic.map((item) =>{return(<li className={styles.resli} key={item.id}> <img className={styles.resimg}...