jQuery .fadeTo()

The .fadeTo() method animates the opacity of the matched elements. It is similar to the .fadeIn() method but that method unhides the element and always fades to 100% opacity.

Durations are given in milliseconds; higher values indicate slower animations, not faster ones. The strings 'fast' and 'slow' can be supplied to indicate durations of 200 and 600 milliseconds, respectively. If any other string is supplied, the default duration of 400 milliseconds is used. Unlike the other effect methods, .fadeTo() requires that duration be explicitly specified.

If supplied, the callback is fired once the animation is complete. This can be useful for stringing different animations together in sequence. The callback is not sent any arguments, but this is set to the DOM element being animated. If multiple elements are animated, it is important to note that the callback is executed once per matched element, not once for the animation as a whole.

We can animate any element, such as a simple image:

<div id="clickme">
 Click here
</div>
<img id="book" src="book.png" alt="" width="100" height="123">
// With the element initially shown, we can dim it slowly:
$( "#clickme" ).click(function() {
 $( "#book" ).fadeTo( "slow" , 0.5, function() {
 // Animation complete.
 });
});

With duration set to 0, this method just changes the opacity CSS property, so .fadeTo( 0, opacity ) is the same as .css( "opacity", opacity ).