jQuery animate problems

Question

I use the following snippet to make an element's background lightblue, then slowly fade to whiite over 30 seconds:

$("#" + post.Id).css("background-color", "lightblue")
.animate({ backgroundColor: "white" }, 30000);

Two questions.

First, instead of fading to white, is there a way to fade opacity to 100%? That way I don't have to change "white" if I choose to change the page's background color?

Second, about once out of every 10 or 15 times, the background stays lightblue and fails to fade to white. I'm using the latest versions of jQuery and the UI core. What could be going wrong?

EDIT: Bounty is for a solution to problem regarding second question.

EDIT2:

Apparently I got downvoted into oblivion because I said I rolled my own solution but didn't show it. My bad. I didn't want to be self-promoting. My code works 100% of the time and doesn't require jQuery. A demonstration and the code can be found at:

http://prettycode.org/2009/07/30/fade-background-color-in-javascript/

Answer 1

Animate only works for numbers. See the jquery docs. You can do opacity but you can't do background color. You can use the color plug in. Background-color uses strings like 'red', 'blue', '#493054' etc... which are not numbers.

Answer 2

What about:

$("#" + post.Id).fadeIn( "slow" );

Answer 3

I'll answer your first question. You can animate opacity like this:

.animate({opacity: 1.0}, 3000)

I think you can try using fadeOut/fadeIn too..

Answer 4

Dont forget the color plugin.

See here

When the color fails to animate to blue you could try to use the callback function to log a message to the console. You can then check that the event actually fired and completed. If it does then you could potentially use two animates. The first one to animate to a halfway house color then the use the callback to animate to white (so you get two bites of the cherry, if the outer fails but completes the callback has a second go)

It would be good if you could try to recreate the issue or give a url of the issue itself.

e.g

$("#" + post.Id).css("background-color", "lightblue")
   .animate({ backgroundColor: "#C0D9D9" }, 15000, function(){
      $(this).animate({ backgroundColor: "#ffffff" }, 15000)
});

Answer 5

You could possibly have two divs that occupy the same space (using position: absolute; and position: relative; setting the z-index on one higher to make sure one is above and the other is below. the top one would have a transparent background and the one below would have a background color. then just fadeout the one below.

Answer 6

You could always use something like this, avoiding the JQuery animate method entirely.

setTimeout(function() { UpdateBackgroundColor(); }, 10);

UpdateBackgroundColor() {
    // Get the element.
    // Check it's current background color.
    // Move it one step closer to desired goal.
    if (!done) {
        setTimeout(UpdateBackgroundColor, 10);
    }
}

Also, you may be able to remove the "white" coding by reading the background color from the appropriate item (which may involve walking up the tree).

Answer 7

I simply rolled my own and got it working correctly.

Answer 8

For your second question: in my experience this is usually because a Javascript error has occurred somewhere else on the page. Once there is one Javascript exception, the rest of the page stops running Javascript. Try installing Firebug (if you haven't already), then open up the "Console" tab and enable it. Then any javascript errors or exceptions will be printed to the console.

Another thing to try (which kinda contradicts my last statement...) is to disable all your browser plug-ins to see if you can recreate. Sometimes they interfere with scripts on the page (particularly GreaseMonkey.)

If you could provide a sample HTML snippet which reproduces this animation problem it would be a lot easier for us to help you. In the script I have pasted below, I can click it all day, as fast or slow as I like, and it never fails to animate for me.

---

For the first question: I know you said you'd found a workaround, but the following works for me (even on IE6) so I thought I'd post it, since it may be different from what you were thinking. (Note that setting CSS "opacity" property through jQuery.css() works on IE, whereas IE does not support the "opacity" property directly in CSS.)

<html>
<head>
<style>
body { background-color: #08f; }
#test { background-color: white; width: 100px; }
</style>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"&gt;&lt;/script&gt;
<script>
var myOpacity = 0.125;
$(function(){
  $('#test').css('opacity', myOpacity);
  $('a').click(function(){
    myOpacity = 1.0 - myOpacity;
    $('#test').animate({ opacity: myOpacity });
    return false;
  });
});
</script>
</head>
<body>
<p><a href="#">Click me</a></p>
<div id="test">Test</div>
</body></html>

Answer 9

As for the second question:

If you think the default animation classes from JQuery are not properly working you could try Bernie's Better Animation Class. I have some good experiences with that library.

Answer 10

It is possible to have jQuery change the Opacity CSS property of an item (as mentioned in another answer), but there's two reasons why that wouldn't work for your scenario. Firstly, making something "100% opaque" is fully visible. If the item didn't have any other modifications to its opacity, the default opacity is 100%, and there would be no change, so I'm guessing you meant fading to 0% opacity, which would be disappearing. This would get rid of the light blue background, but also the text on top of it, which I don't think was your intent.

A potentially easy fix for your situation is to change the color word "white" to "transparent" in your original code listing. The color plugin may not recognize that color word (haven't checked documentation on that yet), but setting the background color to "transparent" will let whatever color behind it (page background, if nothing else) shine through, and will self-update if you change your page background.