start & stop / pause setInterval with javascript,

问题:

I'm trying to pause, and then play, a setInterval loop.

After I have stopped the loop, the "start" button in my attempt doesn't seem to work :

HTML:

<input type="number" id="input" />
<input type="button" onclick="clearInterval(add)" value="stop"/>
<input type="button" onclick="start()" value="start"/>

JS:

input = document.getElementById("input");
function start() {
    add = setInterval("input.value++",1000);
}start();

Is there a better / working way to do this? Your free to use jQuery.

Thanks!

回答1:

The reason you're seeing this specific problem:

jsFiddle wraps your code in a function, so start() is not defined in the global scope.

---

Moral of the story: don't use inline event bindings. Use addEventListener/attachEvent.

---

Other notes:

Please don't pass strings to setTimeout and setInterval. It's eval in disguise.

Use a function instead, and get cozy with var and white space:

var input = document.getElementById("input"),
    add;

function start() {
    add = setInterval(function () {
        input.value++;
    }, 1000);
}

start();

回答2:

See Working Demo on jsFiddle: http://jsfiddle.net/qHL8Z/3/

HTML

<input type="number" id="input" />
<input id="stop" type="button" value="stop"/>
<input id="start" type="button" value="start"/>

Javascript

$(function() {
    var timer = null, 
        interval = 1000,
        value = 0;

    $("#start").click(function() {
      if (timer !== null) return;
      timer = setInterval(function () {
          $("#input").val(++value);
      }, interval); 
    });

    $("#stop").click(function() {
      clearInterval(timer);
      timer = null
    });
});

回答3:

As you've tagged this jQuery ...

First, put IDs on your input buttons and remove the inline handlers:

<input type="number" id="input" />
<input type="button" id="stop" value="stop"/>
<input type="button" id="start" value="start"/>

Then keep all of your state and functions encapsulated in a closure:

EDIT updated for a cleaner implementation, that also addresses @Esailija's concerns about use of setInterval().

$(function() {
    var timer = null;
    var input = document.getElementById('input');

    function tick() {
        ++input.value;
        start();        // restart the timer
    };

    function start() {  // use a one-off timer
        timer = setTimeout(tick, 1000);
    };

    function stop() {
        clearTimeout(timer);
    };

    $('#start').bind("click", start); // use .on in jQuery 1.7+
    $('#stop').bind("click", stop);

    start();  // if you want it to auto-start
});

This ensures that none of your variables leak into global scope, and can't be modified from outside.

(Updated) working demo at http://jsfiddle.net/alnitak/Q6RhG/

回答4:

add is a local variable not a global variable try this

var add;
var input = document.getElementById("input");
function start() {
    add = setInterval("input.value++",1000);
}start();

回答5:

(function(){
    var i = 0;
    function stop(){
        clearTimeout(i);
    }

    function start(){
        i = setTimeout( timed, 1000 );
    }

    function timed(){
       document.getElementById("input").value++;
       start();
    }

    window.stop = stop;
    window.start = start;
})()

http://jsfiddle.net/TE3Z2/

回答6:

You can't stop a timer function mid-execution. You can only catch it after it completes and prevent it from triggering again.