How to pause and resume a javascript timer [duplicate]

问题

I have this timer which works fine, but i need to be able to pause and resume it after that. i would appreciate it if someone could help me.

<html>
<head>
<script>
function startTimer(m,s)
    {
        document.getElementById('timer').innerHTML= m+":"+s;
        if (s==0)
            {
               if (m == 0)
                {
                    return;
                }
                else if (m != 0)
                {
                    m = m-1;
                    s = 60;
                }
        }
    s = s-1;
    t=setTimeout(function(){startTimer(m,s)},1000);
}


</script>
</head>

<body>
<button onClick = "startTimer(5,0)">Start</button>

<p id = "timer">00:00</p>
</body>
</html>

回答1:

I simply can't stand to see setTimeout(...,1000) and expecting it to be exactly 1,000 milliseconds. Newsflash: it's not. In fact, depending on your system it could be anywhere between 992 and 1008, and that difference will add up.

I'm going to show you a pausable timer with delta timing to ensure accuracy. The only way for this to not be accurate is if you change your computer's clock in the middle of it.

function startTimer(seconds, container, oncomplete) {
    var startTime, timer, obj, ms = seconds*1000,
        display = document.getElementById(container);
    obj = {};
    obj.resume = function() {
        startTime = new Date().getTime();
        timer = setInterval(obj.step,250); // adjust this number to affect granularity
                            // lower numbers are more accurate, but more CPU-expensive
    };
    obj.pause = function() {
        ms = obj.step();
        clearInterval(timer);
    };
    obj.step = function() {
        var now = Math.max(0,ms-(new Date().getTime()-startTime)),
            m = Math.floor(now/60000), s = Math.floor(now/1000)%60;
        s = (s < 10 ? "0" : "")+s;
        display.innerHTML = m+":"+s;
        if( now == 0) {
            clearInterval(timer);
            obj.resume = function() {};
            if( oncomplete) oncomplete();
        }
        return now;
    };
    obj.resume();
    return obj;
}

And use this to start/pause/resume:

// start:
var timer = startTimer(5*60, "timer", function() {alert("Done!");});
// pause:
timer.pause();
// resume:
timer.resume();

回答2:

<p id="timer">00:00</p>
<button id="start">Start</button>
<button id="pause">Pause</button>
<button id="resume">Resume</button>

var timer = document.getElementById("timer");
var start = document.getElementById("start");
var pause = document.getElementById("pause");
var resume = document.getElementById("resume");
var id;
var value = "00:00";

function startTimer(m, s) {
    timer.textContent = m + ":" + s;
    if (s == 0) {
        if (m == 0) {
            return;
        } else if (m != 0) {
            m = m - 1;
            s = 60;
        }
    }

    s = s - 1;
    id = setTimeout(function () {
        startTimer(m, s)
    }, 1000);
}

function pauseTimer() {
    value = timer.textContent;
    clearTimeout(id);
}

function resumeTimer() {
    var t = value.split(":");

    startTimer(parseInt(t[0], 10), parseInt(t[1], 10));
}

start.addEventListener("click", function () {
    startTimer(5, 0);
}, false);

pause.addEventListener("click", pauseTimer, false);

resume.addEventListener("click", resumeTimer, false);

on jsfiddle

There are a whole load of improvements that could be made but I'm sticking with the code that the OP posted for the OP's comprehension.

Here is an extended version to give you further ideas on jsfiddle

来源：https://stackoverflow.com/questions/16134997/how-to-pause-and-resume-a-javascript-timer

标签

javascript

timer

resume