Question

New to javascript and such, trying to create a loop for fading logos using jquery.

I’ve got it cycling through them just fine. But i tried to make the loop continuous; so that when it reached the last logo it went back to the beginning, by resetting my for-counter to 0 every time it reached the last logo. This resulted in an infinite loop i think that crashed my browser. So i did a quick google and discovered the window.setInterval(…) timer function.

My problem is, now that firing the looping code relies on timing, i can’t figure out how to calculate the interval time. For reference here’s the code that fades the logos in and out (before trying to loop it):

$(document).ready(function (){

    var fadeDuration = 1000;
    var timeBetweenFade = 2000;
    var totalTimePerChange = fadeDuration + timeBetweenFade;
    var totalLogos = $('.logo').length;
    var currentLogo;
    var i;

        for(i = 0; i < totalLogos; i++)
        {
            currentLogo = "#img" + i;
            if(i == 0){
                $(currentLogo).fadeIn(fadeDuration).delay(timeBetweenFade).fadeOut(fadeDuration);
                }
            else{ //general case
                $(currentLogo).delay(totalTimePerChange * i).fadeIn(fadeDuration).delay(timeBetweenFade).fadeOut(fadeDuration);
            }
        }
});

I tried to get the time a complete loop took in a couple of ways:

$(document).ready(function (){

    //..declarations..

    window.setInterval( function() {
        //..FOR LOOP HERE..
    }, i*(fadeDuration + timeBetweenFade + fadeDuration));
});

//I also tried..

$(document).ready(function (){

    //..declarations..
    var timeTakenToLoop;
    var startLoopTime;

    window.setInterval( function() {
    startLoopTime = new Date().getTime();
        //...FOR LOOP HERE..
    timeTakenToLoop = new Date().getTime() - startLoopTime;
    }, timeTakenToLoop);
});

But in both cases I get logos starting to overlap as the function calls timing is wrong. Could someone with a bit more experience suggest what the best approach would be?

Oh and just in case anyone needs it to understand the javascript, here’s the html to match..

    <div id="img0" class="logo">
    <img src="{% static "CSS/Images/phone_icon.gif" %}"/>
    </div>
    <div id="img1" class="logo">
    <img src="{% static "CSS/Images/email_icon.gif" %}"/>
    </div>
    <div id="img2" class="logo">I can fade too</div>

Answer 1

Simple jQuery approach, no setTimeout and no setInterval.

var loop = function(idx, totalLogos) {
  var currentLogo = "#img" + idx;
  $(currentLogo)
    .delay(currentLogo)
    .fadeIn(fadeDuration)
    .delay(currentLogo)
    .fadeOut(fadeDuration, function(){
      loop( (idx + 1) % totalLogos, totalLogos);
    });
}
loop(0, $('.logo').length);​

See it here.