[javascript] How to start and stop/pause setInterval?

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 :

_x000D_
_x000D_
input = document.getElementById("input");_x000D_
_x000D_
function start() {_x000D_
  add = setInterval("input.value++", 1000);_x000D_
}_x000D_
start();
_x000D_
<input type="number" id="input" />_x000D_
<input type="button" onclick="clearInterval(add)" value="stop" />_x000D_
<input type="button" onclick="start()" value="start" />
_x000D_
_x000D_
_x000D_

Is there a working way to do this?

This question is related to javascript jquery loops setinterval

The answer is


(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/


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

_x000D_
_x000D_
$(function() {_x000D_
  var timer = null,_x000D_
    interval = 1000,_x000D_
    value = 0;_x000D_
_x000D_
  $("#start").click(function() {_x000D_
    if (timer !== null) return;_x000D_
    timer = setInterval(function() {_x000D_
      $("#input").val(++value);_x000D_
    }, interval);_x000D_
  });_x000D_
_x000D_
  $("#stop").click(function() {_x000D_
    clearInterval(timer);_x000D_
    timer = null_x000D_
  });_x000D_
});
_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>_x000D_
<input type="number" id="input" />_x000D_
<input id="stop" type="button" value="stop" />_x000D_
<input id="start" type="button" value="start" />
_x000D_
_x000D_
_x000D_


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


add is a local variable not a global variable try this

_x000D_
_x000D_
var add;_x000D_
var input = document.getElementById("input");_x000D_
_x000D_
function start() {_x000D_
  add = setInterval("input.value++", 1000);_x000D_
}_x000D_
start();
_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>_x000D_
<input type="number" id="input" />_x000D_
<input type="button" onclick="clearInterval(add)" value="stop" />_x000D_
<input type="button" onclick="start()" value="start" />
_x000D_
_x000D_
_x000D_


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/


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