不多說直接上程式碼：

var stime = 16,
    t;

function fntime() {
    stime--;
    t = setTimeout(fntime, 1000);
    if (stime < 0) {
        clearTimeout(t);
        return;
    }

    console.log(stime);
}

var timer = function() {
    try {
        if (t._idleTimeout < 0) {
            fntime();
            console.log(1
 
);
        }
        console.log(2);
    } catch (e) {
        fntime();
        console.log(3);
    }

}

timer();
timer();

console.log(t);
console.log(t._idleTimeout);
clearTimeout(t);
console.log(t);
console.log(t._idleTimeout);


timer();
timer();