Language Java Script Definitive Examples 16.1.TXT

 <!-- This example is from the book _JavaScript: The Definitive Guide_.     -->
<!-- Written by David Flanagan.  Copyright (c) 1996 O'Reilly & Associates. -->
<!-- This example is provided WITHOUT WARRANTY either expressed or implied.-->
<!-- You may study, use, modify, and distribute it for any purpose.        -->

<!-- The image that will be animated.  Give it a name for convenience -->
<IMG SRC="images/0.gif" NAME=animation>

<SCRIPT>
// Create a bunch of off-screen images, and get them started 
// loading the images we're going to animate.
images =index.html new Array(10);
for(var i = 0; i < 10; i++) {
    images[i] =index.html new Image();                 // Create an Image object
    images[i].src = "images/" + i + ".gif";  // tell it what URL to load
}

// Later, when we want to perform our animation, we can use these URLs,
// knowing that they've been loaded into the cache.  Note that we perform
// the animation by assigning the URL, not the Image object itself.
// Also note that we call the image by name, rather than as document.images[0]
function animate()
{
    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; // allows us to stop the animation.
</SCRIPT>

<FORM>                   <!-- Buttons to control the animation -->
  <INPUT TYPE=button VALUE="Start" 
         onClick="if (timeout_id ==index.html null) animate()">
  <INPUT TYPE=button VALUE="Stop" 
         onClick="if (timeout_id) clearTimeout(timeout_id); timeout_id=null;">
</FORM>

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