Framework for creating CSS-based animations
/*
Examples From
JavaScript: The Definitive Guide, Fourth Edition
Legal matters: these files were created by David Flanagan, and are
Copyright (c) 2001 by David Flanagan. You may use, study, modify, and
distribute them for any purpose. Please note that these examples are
provided "as-is" and come with no warranty of any kind.
David Flanagan
*/
<html>
<body>
<script>
/**
* AnimateCSS.js:
* This file defines a function named animateCSS(), which serves as a framework
* for creating CSS-based animations. The arguments to this function are:
*
* element: The HTML element that is to be animated.
* numFrames: The total number of frames in the animation.
* timePerFrame: The number of milliseconds to display each frame.
* animation: An object that defines the animation; described below.
* whendone: An optional function to call when the animation finishes.
* If specified, this function is passed element as its argument.
*
* The animateCSS() function simply defines an animation framework. It is the
* properties of the animation object that specify the animation to be
* done. Each property should have the same name as a CSS style property. The
* value of each property must be a function that returns values for that
* style property. Each function is passed the frame number and the total
* amount of elapsed time, and it can use these to compute the style value it
* should return for that frame. For example, to animate an image so that it
* slides in from the upperleft, you might invoke animateCSS as follows:
*
* animateCSS(image, 25, 50, // Animate image for 25 frames of 50ms each
* { // Set top and left attributes for each frame as follows
* top: function(frame,time) { return frame*8 + "px"; },
* left: function(frame,time) { return frame*8 + "px"; }
* });
*
**/
function animateCSS(element, numFrames, timePerFrame, animation, whendone) {
var frame = 0; // Store current frame number
var time = 0; // Store total elapsed time
// Arrange to call displayNextFrame() every timePerFrame milliseconds.
// This will display each of the frames of the animation.
var intervalId = setInterval(displayNextFrame, timePerFrame);
// The call to animateCSS() returns now, but the line above ensures that
// the nested function defined below will be invoked once for each frame
// of the animation. Because this function is defined inside
// animateCSS(), it has access to the arguments and local variables of
// animateCSS() even though it is invoked after that function has returned!
function displayNextFrame() {
if (frame >= numFrames) { // First, see if we're done
clearInterval(intervalId); // If so, stop calling ourselves
if (whendone) whendone(element); // Invoke whendone function
return; // And we're finished
}
// Now loop through all properties defined in the animation object
for(var cssprop in animation) {
// For each property, call its animation function, passing the
// frame number and the elapsed time. Use the return value of the
// function as the new value of the corresponding style property
// of the specified element. Use try/catch to ignore any
// exceptions caused by bad return values.
try {
element.style[cssprop] = animation[cssprop](frame, time);
} catch(e) {}
}
frame++; // Increment the frame number
time += timePerFrame; // Increment the elapsed time
}
}
animateCSS(image, 25, 50, // Animate image for 25 frames of 50ms each
{ // Set top and left attributes for each frame as follows
top: function(frame,time) { return frame*8 + "px"; },
left: function(frame,time) { return frame*8 + "px"; }
});
</script>
</body>
<html>
Related examples in the same category
