jquery/js : best way to have an image fading in and out? (recursion?)

Is there a better way than this, for two images positioned over each other where #state_2 is the top image.

function recursive_fade(){
    $('#top_img').delay(4000).fadeOut(400).delay(4000).fadeIn(40开发者_Python百科0);
    recursive_fade();                
};

$(function(){
    recursive_fade(); 
});

When i dynatrace this, it seems to use fair bit of cpu...

You should use continuation-style here: let the fx system call the recursive_fade when the last animation has finished:

function recursive_fade(){
    $('#top_img')
         .delay(4000)
         .fadeOut(400)
         .delay(4000)
         .fadeIn(400, recursive_fade );
};

EDIT 2 - meanwhile, it seems (long liveth the jQuery forum) that the Effects are implemented using a queue and the setTimeout function - making EDIT 1 obsolete.

EDIT - since I have no idea if jQuery allows this recursion (I didn't find convincing proof), I think it's best to combine the "Timeout" suggestions with the continuation technique like so:

function recursive_fade(){
    $('#top_img')
         .delay(4000)
         .fadeOut(400)
         .delay(4000)
         .fadeIn(400, function() { setTimeout( recursive_fade, 0 ); } );
};

This offers the guarantee that stack won't blow up, yet avoids the need to calculate the timeout interval.

I wouldn't do it recursively, I would use a setTimeout so it doesnt totally lock up the browser.

function recursive_fade(){
    $('#top_img').delay(4000).fadeOut(400).delay(4000).fadeIn(400);
    setTimeout(function(){recursive_fade(); },8800);               
};

$(function(){
   recursive_fade();
});

How about using setInterval(). Info here.

Something like this:

function fadeShow() {
    $('#top_img').delay(4000).fadeOut(400).delay(4000).fadeIn(400);
}
$(function() {
    setInterval(fadeShow, 8800);
}