如何使用反应钩子设置状态数组 [英] how to set state array using react hooks

问题描述

提前致谢.我有一个如下的状态数组.

Thanks in advance. I have a state array as below.

我需要向状态数组添加一个项目，我发现我们不需要进行状态突变.我如何使用 prevState 设置状态.

I need to add an item to state array, I came across that we need not do state mutation. How do i set state with prevState.

const [messages, setMessages] = React.useState(
        [
            {
                _id: 12,
                createdAt: new Date(),
                text: 'All good',
                user: {
                    _id: 1,
                    name: 'Sian Pol',
                }
            },
            {
                _id: 21,
                createdAt: "2019-11-10 22:21",
                text: 'Hello user',
                user: {
                    _id: 2,
                    name: 'User New'
                }
            }]
    )

如何调用 set State 来附加这个 state 数组.

How to to i call the set State to append this state array.

类似的东西?

setMessages(previousState => ({...stat

谁能帮我获取上面的行代码.

Can anyone help me in getting the above line code.

推荐答案

在列表末尾插入新元素

const addMessage = (newMessage) => setMessages(state => [...state, newMessage])

在列表的开头插入新元素

To insert new element at the begining of the list

const addMessage = (newMessage) => setMessages(state => [newMessage, ...state])

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