基本思路：
1-獲取 當(dāng)前時(shí)間 與 搶購開始時(shí)間 時(shí)間差
2-獲取搶購按鈕 Dom元素
3-設(shè)置 setInterval定時(shí)函數(shù)，計(jì)算臨近搶購時(shí)間前縮小定時(shí)器時(shí)間間隔

function panicCakes(){
    console.log("panic mooncakes");
    document.getElementById('J_LinkBuy').click();
}
//以搶下午12點(diǎn)的為例
var deadline=new Date(2016,10,18,12,0);
var panic=null,diffs=null;
var t=setInterval(function(){
    var now=new Date();
    console.log(deadline)
    console.log(now)
    var    diffms=deadline.getTime()-now.getTime();
    console.log(diffms)
    if(diffms<5001){
        console.log("開始加速...")
        panic=setInterval(panicCakes,50)
    }else{
        diffs=diffms/1000;
        console.log("剩余"+parseInt(diffs/60)+"分"+parseInt(diffs%60)+"秒")
    }
},5000)