13-4.txt

Javascript语言开发经典教程开发

<script>
// Here are the initial values for our animation. 
var x = 0, y = 0, w=200, h=200;  // Window position and size
var dx = 5, dy = 5;              // Window velocity   
var interval = 100;              // Milliseconds between updates

// Create the window that we're going to move around.
// The javascript: URL is simply a way to display a short document.
// The final argument specifies the window size.
var win = window.open('javascript:"<H1>BOUNCE!</H1>"', "", 
		      "width=" + w + ",height=" + h);

// Set the initial position of the window.
win.moveTo(x,y);

// Use setInterval() to call the bounce() method every interval 
// milliseconds. Store the return value so that we can stop the
// animation by passing it to clearInterval().
var intervalID  = window.setInterval("bounce()", interval);

// This function moves the window by (dx, dy) every interval ms.
// It bounces whenever the window reaches the edge of the screen.
function bounce() {
    // If the user closed the window, stop the animation.
    if (win.closed) {
        clearInterval(intervalID);
        return;
    }

    // Have we reached the right or left edge? 
    if ((x+dx > (screen.availWidth - w)) || (x+dx < 0)) dx = -dx;

    // Have we reached the bottom or top edge?
    if ((y+dy > (screen.availHeight - h)) || (y+dy < 0)) dy = -dy;

    // Update the current position of the window.
    x += dx;
    y += dy;

    // Finally, move the window to the new position.
    win.moveTo(x,y);
}
</script>

<!-- Clicking this button stops the animation! -->
<FORM>
<INPUT TYPE=button VALUE="Stop" 
       onClick="clearInterval(intervalID); win.close();">
</FORM>