正确回答答案

var isPlaying = true;
var toHandle = null;

$("#push").click(function () {
    isPlaying = false;
    if (toHandle !== null)
    {
       clearTimeout(toHandle);
       toHandle = null;
    }
});

$("#play").click(function () {
    isPlaying = true;
    show();
});

function show() {
    if (isPlaying) {
        toHandle = null;
        var Digital = new Date();
        var time2 = Digital.getTime();
        var time1 = 1403517957984;
        var diff = Math.abs(new Date(time2) - new Date(time1));
        var seconds = Math.floor(diff / 1000); //ignore any left over units smaller than a second
        var minutes = Math.floor(seconds / 60);
        seconds = seconds % 60;
        var hours = Math.floor(minutes / 60);
        minutes = minutes % 60;
        if (hours < 10) hours = "0" + hours;
        if (minutes < 10) minutes = "0" + minutes;
        if (seconds < 10) seconds = "0" + seconds;
        $('#worked_time').html(hours + ":" + minutes + ":" + seconds);

        toHandle = setTimeout("show()",1000);
    }
}
show();