<!-- This example is from JavaScript: The Definitive Guide, 3rd Edition. -->
<!-- That book and this example were Written by David Flanagan. -->
<!-- They are Copyright (c) 1996, 1997, 1998 O'Reilly & Associates. -->
<!-- This example is provided WITHOUT WARRANTY either expressed or implied.-->
<!-- You may study, use, modify, and distribute it for any purpose, -->
<!-- as long as this notice is retained. -->
<!-- The image that will be animated. Give it a name for convenience. -->
<IMG SRC="images/0.gif" NAME=animation>
<SCRIPT>
// Count how many images have been loaded. When we reach 10, start animating.
function count_images() { if (++num_loaded_images == 10) animate(); }
var num_loaded_images = 0;
// Create the off-screen images and assign the image URLs.
// Also assign an event handler so we can count how many images have been
// loaded. Note that we assign the handler before the URL, because otherwise
// the image might finish loading (e.g., if it is already cached) before
// we assign the handler, and then we'll lose count of how many have loaded!
var images = new Array(10);
for(var i = 0; i < 10; i++) {
images[i] = new Image(); // Create an Image object.
images[i].onload = count_images; // Assign the event handler.
images[i].src = "images/" + i + ".gif"; // Tell it what URL to load.
}
function animate() // The function that does the animation.
{
document.animation.src = images[frame].src;
frame = (frame + 1)%10;
timeout_id = setTimeout("animate()", 250); // Display next frame later.
}
var frame = 0; // Keep track of what frame of the animation we're on.
var timeout_id = null; // This allows us to stop the animation.
</SCRIPT>
<!-- Buttons to control the animation. Note that we don't let the user
-- start the animation before all the images are loaded. -->
<FORM>
<INPUT TYPE=button VALUE="Start"
onClick="if (timeout_id==null && num_loaded_images==10) animate()">
<INPUT TYPE=button VALUE="Stop"
onClick="if (timeout_id) clearTimeout(timeout_id); timeout_id=null;">
</FORM>
