之前一直在用vuejs,因?yàn)樽罱_(kāi)發(fā)要用到reactjs
但是發(fā)現(xiàn)他沒(méi)有vuejs這種可以watch數(shù)據(jù)對(duì)象的方法，
請(qǐng)問(wèn)下有過(guò)reactjs開(kāi)發(fā)經(jīng)驗(yàn)的人，如果我想監(jiān)聽(tīng)一個(gè)state里的某個(gè)屬性變化要怎么做？
我現(xiàn)在有個(gè)例子因?yàn)槭嵌〞r(shí)器的關(guān)系，在里面用了setState然后執(zhí)行后會(huì)一直報(bào)
Warning: setState(...): Can only update a mounted or mounting component. This usually means you called setState() on an unmounted component. This is a no-op. Please check the code for the Main component.
我想把他拿出來(lái)，但是如果沒(méi)有監(jiān)聽(tīng)某個(gè)值又不知道怎么放出來(lái)

class Main extends React.Component {
        constructor() {
            super();
            this.isCancelTimer = false;
            this.state = {
                isTimeOut: false,
                isSubmit: true
            };
        }
        
        setTimer(severTime) {
            let currentDate = 0,
                timer = null,
                newSeverTime = '',
                counter =()=>{

                    if (currentDate <= 0 || this.isCancelTimer) {
                        clearTimeout(timer);
                        //這里的setState怎么拿到外面
                        this.setState(Object.assign(this.state, {
                            isTimeOut: true,
                            isSubmit: false
                        }))
                    }
                    currentDate--;
                    timer = setTimeout(() => {
                        let day = Math.floor(currentDate / 60 / 60 / 24),
                            hours = Math.floor(currentDate / 60 / 60 % 24),
                            minutes = Math.floor(currentDate / 60 % 60),
                            seconds = currentDate % 60;
                        if (!this.isCancelTimer) {
                            this.setState(Object.assign({}, this.state, {
                                timer: (''+day).padStart(2, 0)+'天'+(''+hours).padStart(2, 0)+'時(shí)'+(''+minutes).padStart(2, 0)+'分'+(''+seconds).padStart(2, 0)+'秒'
                            }));
                        }
                        counter();
                    }, 1000);
                };
            // 適配IOS
            newSeverTime = severTime.replace(/-/g, (value) => '/');
            currentDate = +((+new Date(newSeverTime) - (+new Date())) / 1000).toFixed(0);
            currentDate = currentDate.toFixed(0);
            counter();
        }
        componentDidMount() {
            this.setTimer('2017-11-18 17:10:50')
        }
    }