Reactjs 未捕获类型错误：无法读取属性'；长度'；从道具中未定义的属性

我累得太久了

关于下面的代码，当我从state获取members对象时，它不会被识别为数组对象

所以我从复制文本中编写了dummy_成员，它工作并被识别为数组对象

    render() {
        const members = this.props.members; // <- Get from state.
        console.log(members); //Show Array Object (1)
        console.log(members.length); //Error

        const dummy_members = [{xx:xxx},..]; // <- Copied & paste text from JSON data on browser from server.
        console.log(dummy_members); // Show Array Object (2)
        console.log(dummy_members.length); // It shows array length.

这似乎没有错

我的问题是，成员（1）和伪_成员（2）都有相同的控制台日志，但结果不同。props（1）中的成员未被识别为数组

我想从this.props.members获取members对象

---

谢谢。

如果

reducer01

不总是包含

成员

数组，则

const members=reducer01。成员

将未定义且

成员。长度

将抛出您观察到的错误

为了防止未定义，可以使用

console.log（members&&members.length）

---

（为了帮助您修复减速机，您必须在您的问题中共享减速机的代码。）

它是数组还是类似数组的对象您知道如何识别它们吗？或者如何将它们转换为另一个对象？您可以使用数组的

isArray

进行检查。如果道具数据来自异步操作，初始渲染中没有道具数据。因此它抛出一个错误。const initData={members:[]，}导出函数reducer01（state=initData，action）{switch（action.type）{case'GET_members'：返回{…state，members:action.members}；默认值：返回状态；}请添加负责获取数据的

MapStateTops（）

方法和

Action creator

，我想你是对的。但是我该怎么办呢。我的理解是在

this初始化。state={members:[]}

就足够了。这是我的误解吗？现在我的代码有

导出默认连接（（状态）=>state）（第01页）

初始状态仅使用一次，如果

action.members

未定义，则无论初始化如何，还原程序都将返回一个状态为

{members:undefined}

(12) [{…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}]
0: {away_team_ot_score: 0, away_team_ot_shots: 0, away_team_p1_score: 3, away_team_p1_shots: 20, away_team_p2_score: 4, …}
1: {away_team_ot_score: 0, away_team_ot_shots: 0, away_team_p1_score: 1, away_team_p1_shots: 13, away_team_p2_score: 2, …}
2: {away_team_ot_score: 0, away_team_ot_shots: 0, away_team_p1_score: 1, away_team_p1_shots: 15, away_team_p2_score: 2, …}
3: {away_team_ot_score: 0, away_team_ot_shots: 0, away_team_p1_score: 2, away_team_p1_shots: 15, away_team_p2_score: 3, …}
4: {away_team_ot_score: 0, away_team_ot_shots: 0, away_team_p1_score: 6, away_team_p1_shots: 23, away_team_p2_score: 9, …}
5: {away_team_ot_score: 0, away_team_ot_shots: 0, away_team_p1_score: 0, away_team_p1_shots: 10, away_team_p2_score: 2, …}
6: {away_team_ot_score: 0, away_team_ot_shots: 0, away_team_p1_score: 1, away_team_p1_shots: 12, away_team_p2_score: 1, …}
7: {away_team_ot_score: 0, away_team_ot_shots: 0, away_team_p1_score: 1, away_team_p1_shots: 19, away_team_p2_score: 1, …}
8: {away_team_ot_score: 0, away_team_ot_shots: 0, away_team_p1_score: 0, away_team_p1_shots: 10, away_team_p2_score: 2, …}
9: {away_team_ot_score: 0, away_team_ot_shots: 0, away_team_p1_score: 3, away_team_p1_shots: 16, away_team_p2_score: 4, …}
10: {away_team_ot_score: 0, away_team_ot_shots: 0, away_team_p1_score: 0, away_team_p1_shots: 8, away_team_p2_score: 1, …}
11: {away_team_ot_score: 0, away_team_ot_shots: 0, away_team_p1_score: 0, away_team_p1_shots: 8, away_team_p2_score: 1, …}
length: 12