参考文章链接：https://www.jianshu.com/p/6e4888d8d252

    componentDidMount() {

        this.setState({

            count: this.state.count + 1

        });

        console.log('1',this.state.count)

        setTimeout(() => {

            console.log('2',this.state.count)

            this.setState({

                count: this.state.count + 1

            })

            console.log('3',this.state.count)

        }, 0);

        this.setState({

            count: this.state.count + 1

        });

        console.log('4',this.state.count)

    }

只有在setTimeout(()=>{

           this.setState({

                    才起作用

      })

},0)