this.state = {
    btnText: ‘获取验证码‘,timer: 5,discodeBtn: false,clearInterval: false
}
let siv = setInterval(() => {
    this.setState({ timer: (timer--),btnText: timer,discodeBtn: true },() => {
        if (timer === 0) {
            clearInterval(siv);
            this.setState({ btnText: ‘重新发送‘,discodeBtn: false })
        }
    });
},1000);