反应，setState 在我的反应应用程序中不起作用

Question

这是我的代码：

import React, { Component } from 'react';

class Counter extends Component {
    constructor(props){
        super(props);
        this.state = {
            number : 0
        };

        this.handleIncrease = this.handleIncrease.bind(this);
        this.handleDecrease = this.handleDecrease.bind(this);
    }

    handleIncrease = () => {
        this.setState=({
            number: this.state.number + 1
        });
        console.log("handleIncrease()");
    }
    handleDecrease = () => {
        this.setState({
            number: this.state.number - 1
        });
        console.log("handleDecrease()");
    }

    render(){
        return (
            <div>
                <hr/>
                <h1>Counter</h1>
                <p>number : {this.state.number}</p>
                <button onClick={this.handleIncrease}>+</button>
                <button onClick={this.handleDecrease}>-</button>
                <hr/>
            </div>
        )
    }
}

export default Counter;

当我按下 - 按钮时它有效，但当我按下 + 按钮时它不起作用并且出现错误：

TypeError: _this.setState is not a function Counter._this.handleDecrease

Answer 1

import React, { Component } from 'react';

class Counter extends Component {
    constructor(props){
        super(props);
        this.state = {
            number : 0
        };

        this.handleIncrease = this.handleIncrease.bind(this);
        this.handleDecrease = this.handleDecrease.bind(this);
    }

    handleIncrease = () => {
       //here remove equal
        this.setState({
            number: this.state.number + 1
        });
        console.log("handleIncrease()");
    }
    handleDecrease = () => {
        this.setState({
            number: this.state.number - 1
        });
        console.log("handleDecrease()");
    }

    render(){
        return (
            <div>
                <hr/>
                <h1>Counter</h1>
                <p>number : {this.state.number}</p>
                <button onClick={this.handleIncrease}>+</button>
                <button onClick={this.handleDecrease}>-</button>
                <hr/>
            </div>
        )
    }
}

export default Counter;

Answer 2

去掉等号：

handleIncrease = () => {
    >>>> this.setState({
       number: this.state.number + 1
     });
     console.log("handleIncrease()");
    }

此外，当使用先前的状态设置新状态时，在 setState 中传递一个函数，因为状态更新可以是异步的。

更多信息：https://reactjs.org/docs/state-and-lifecycle.html

反应，setState 在我的反应应用程序中不起作用

react, setState does not work in my react app

javascript

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reactjs