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I'm new to javascript and am trying to call a function using setTimeout from within a for loop. The loop executes for each member of a nodeList.

I'm finding that the function I'm calling with setTimeout is only actually executing during the last iteration of the loop. In the example below, I would like to make three separate calls to setTimeout but I'm finding that the first two calls are ignored.

function moveants(e, stepdistance) {

    . . . . .

    for(var i = 0; i < 3; i++)
    {
        var nextAnt = antgroup.childNodes[i]
        nextAnt.count = 0;
        nextAnt.member = i;
        setTimeout(function () { takeStep(nextAnt, mouseclickX, mouseclickY, 10) }, 0);
    }
}

function takeStep(ant, destX, destY, stepDistance) {

    . . . .

    . . . .

    if( condition )
    {
        return;
    }
    else
    {
        takeStep(ant, destX, destY, stepDistance);
    }
}

I have seen other posts that describe making multiple calls to setTimeout. Amazingly (to me), the multiple calls will work if I simply take them out of the for loop like this.

    setTimeout(function () { takeStep(antgroup.childNodes[0], 
         mouseclickX, mouseclickY, 10) }, 10);
    setTimeout(function () { takeStep(antgroup.childNodes[1], 
         mouseclickX, mouseclickY, 10) }, 10);
    setTimeout(function () { takeStep(antgroup.childNodes[2], 
         mouseclickX, mouseclickY, 10) }, 10);

I just can't figure out why there is a difference between calling them from within a for loop and calling them outside of one.

I am getting valid return values from the setInterval call in every case.. it's just that with only the last iteration of the for loop does the function actually execute.

Thanks in advance for any help.

I'm new to javascript and am trying to call a function using setTimeout from within a for loop. The loop executes for each member of a nodeList.

I'm finding that the function I'm calling with setTimeout is only actually executing during the last iteration of the loop. In the example below, I would like to make three separate calls to setTimeout but I'm finding that the first two calls are ignored.

function moveants(e, stepdistance) {

    . . . . .

    for(var i = 0; i < 3; i++)
    {
        var nextAnt = antgroup.childNodes[i]
        nextAnt.count = 0;
        nextAnt.member = i;
        setTimeout(function () { takeStep(nextAnt, mouseclickX, mouseclickY, 10) }, 0);
    }
}

function takeStep(ant, destX, destY, stepDistance) {

    . . . .

    . . . .

    if( condition )
    {
        return;
    }
    else
    {
        takeStep(ant, destX, destY, stepDistance);
    }
}

I have seen other posts that describe making multiple calls to setTimeout. Amazingly (to me), the multiple calls will work if I simply take them out of the for loop like this.

    setTimeout(function () { takeStep(antgroup.childNodes[0], 
         mouseclickX, mouseclickY, 10) }, 10);
    setTimeout(function () { takeStep(antgroup.childNodes[1], 
         mouseclickX, mouseclickY, 10) }, 10);
    setTimeout(function () { takeStep(antgroup.childNodes[2], 
         mouseclickX, mouseclickY, 10) }, 10);

I just can't figure out why there is a difference between calling them from within a for loop and calling them outside of one.

I am getting valid return values from the setInterval call in every case.. it's just that with only the last iteration of the for loop does the function actually execute.

Thanks in advance for any help.

• javascript
• for-loop
• settimeout

Share Improve this question Follow edited May 23, 2017 at 12:22 CommunityBot 111 silver badge asked May 13, 2011 at 2:12 Michael PhillipsMichael Phillips 15633 silver badges77 bronze badges 2

• As Dark Slipstream says: you have 0 in the delay for a timeout Try it with a delay eg setTimeout(function () { takeStep(nextAnt, mouseclickX, mouseclickY, 10) }, 10); – James Khoury Commented May 13, 2011 at 2:24
• I apologize. I was setting delay of 10 inside the loop as well but I accidentally deleted the time parameter in the post. – Michael Phillips Commented May 13, 2011 at 12:34

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2 Answers 2

Sorted by: Reset to default 8

nextAnt will be overwritten on every loop, so takeStep() will be called 3 times, but always with the same arguments.

You may try this instead:

(function(a,b,c){
     setTimeout(function(){
                           takeStep(a,b,c,10)}, 0);
      })(nextAnt, mouseclickX, mouseclickY);

If your not setting a delay, then why bother with setTimeout?

In the loop your delay is set to 0, outside the loop you've used 10. Also, outside the loop you've assigned values to count and member, but not outside the loop?

Try this:

function moveants(e, stepdistance)
{
    for (var i = 0; i < 3; i++)
    {
        setTimeout("takeStep(antgroup.childNodes[i], mouseclickX, mouseclickY, 10)", 0);
    }
}

or this:

function moveants(e, stepdistance)
{
    for (var i = 0; i < 3; i++)
    {
        takeStep(antgroup.childNodes[i], mouseclickX, mouseclickY, 10);
    }
}

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