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Programming the Scroller
How much programming does it take to create a scroller? Twenty lines, to be exact, as you will see. But before we go into the code, let us understand what features of JavaScript makes the scroller possible.
First is the ability to write to the status bar using
the window.status property like this:
window.status = "This will appear in the status bar"
The second is the setTimeout() function. This function takes two parameters. The first is a string specifying the JavaScript statement to be executed on triggering and the second is a number specifing time in milliseconds after which triggering occurs.
Our scroller is essentially a function which, on each invocation, moves the text on the scroll bar a little to the left and then calls setTimeout() to invoke itself after a small interval of time.
Here is the complete code for the scroller.
<SCRIPT LANGUAGE="JavaScript">
<!-- Start of scroller script
var scrollCounter = 0;
var scrollText = "Any text here";
var scrollDelay = 70;
var i = 0;
while (i ++ < 140)
scrollText = " " + scrollText;
function Scroller()
{
window.status = scrollText.substring(scrollCounter++,
scrollText.length);
if (scrollCounter == scrollText.length)
scrollCounter = 0;
setTimeout("Scroller()", scrollDelay);
}
Scroller();
// End of scroller script -->
</SCRIPT>
The only other function we use is substring() which
is a method of the string object. If name="JavaScript",
then name.substring(4,9) will return "Script".
You get the general idea, right?
