Incorrect usage of setTimeout?

Question

I've written a script that fires off 2 URLs based on some random number logic and I'm trying to set a delay before either one is fired (of half a second) but I don't think it's working properly. Am I doing this correctly? Code is below:

var clicks  = "http://www.urlone.com";
var impressions = "http://www.urltwo.com";
var randomNumber = (Math.random()*100);

function callOut() {
for (var i = 0; i < lengthVal; i++){
    if (randomNumber < 75) { 
        var randomCounter = (Math.random()*100);
            if (randomCounter < 50) {
                setTimeout("image1.src = clicks;",500);

            }
            else if (randomCounter > 50) {
                setTimeout("image1.src = impressions;",500);                    
            }
    }
    }
}

Yes it's wrong. Use function(){ ... } instead of " ... ". And, do not use a loop, but a function + counter (currently, all of your methods fire together after a half second). — Rob W
– Rob W, Commented Feb 22, 2012 at 15:32
what is clicks and impressions? use setTimeout(function(){image1.src=clicks;}, 500); — silly
– silly, Commented Feb 22, 2012 at 15:32
@RobW I've had to "answer my own question" but of course using all this excellent advice. Thanks to all for answers/comments though — zik
– zik, Commented Feb 22, 2012 at 16:45
Your function could never work, because you're not passing a function to setTimeout. Want me to edit your answer, or post a new one? — Rob W
– Rob W, Commented Feb 22, 2012 at 16:47

gdoron · Accepted Answer · 2012-02-22 15:33:55Z

1

setTimeout first parameter should be a function. Not string of code.

code in the alternate syntax, is a string of code you want to execute after delay milliseconds. (Using this syntax is not recommended for the same reasons as using eval())

MDN

setTimeout(function(){...}, 500);

answered Feb 22, 2012 at 15:33

gdoron

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3 Comments

MMM Over a year ago

A string containing code works too and is valid according to standards. Why are you saying it should be a function name (I take you mean a function reference)?

MMM Over a year ago

It is valid and completely legal though. Moreover eval is evil only when used with strings concatenated with variables (e.g. eval("myvar = " + number)).

MMM Over a year ago

Yes, and I am questioning that. I know that you did not write "must", but I don't see a reason why it "should" (as I've explained earlier). Let's say we differ in opinions.

fmsf · Accepted Answer · 2012-02-22 15:35:29Z

1

Taken from here: http://www.codescream.com/?p=18 read it it should help :)

If you want to make a delay with setTimeout you should do exactly this:

setTimeout( function () {
      doThings()
}, 1000);

and never this:

setTimeout( "doThings()", 1000);

answered Feb 22, 2012 at 15:35

fmsf

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Comments

PiTheNumber · Accepted Answer · 2012-02-22 15:37:09Z

0

setTimeout("image1.src = clicks;",500);

For this image1 must be declared in a global context, like this:

var image1 = document.getElementById('image1');

But you better use a function here.

function setImageSrcClicks(){
    document.getElementById('image1').src = 'http://clicks_url';
}
setTimeout(setImageSrcClicks,500);

answered Feb 22, 2012 at 15:37

PiTheNumber

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2 Comments

zik Over a year ago

Sorry I left this out - it has already been declared, I've just left it out for some bizzare reason :S

PiTheNumber Over a year ago

If it's not working image1 or clicks is not declared. For debugging try setTimeout("console.log(image1, clicks);",500);

zik · Accepted Answer · 2012-02-23 09:55:12Z

Duly noted about using setTimeout with a string. Here is how I ended up doing it. Is this the 'best' way to do this?

var clicks = "http://www.urlone.com";
var impressions = "http://www.urltwo.com";
var conversions = "http://www.urlthree";
var lengthVal = (Math.random() * 20 + 20);
var image1 = new Image();
var image2 = new Image();
var globalCounter = -1;



function callOut() {
    var ord = (Math.random() * 9999999999999) + "";

    var randomNumber = (Math.random() * 100);  // Random value for each call
    if (randomNumber < 75) {
        var randomCounter = Math.random() * 100;
        alert(randomCounter);
        if (randomCounter < 50) {
            image1.src = clicks + ord + "?";
        }
        if (randomCounter > 50) {
            image2.src = impressions + ord + "?";
        }
    }
    if (globalCounter++ < lengthVal) {
        setTimeout(callOut, 1000); // Call itself after another second
    }
}

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