HTML and CSS Reference
In-Depth Information
A function called scroller() is defined.
This looks kind of tricky, but here's what's happening. The substr() method ex-
tracts everything between the first character and the rest of the string substr ( 1,
str.length ), resulting in “ nly 19 shopping days left until Christmas! ”. Next, another
subtsr(0,1) method extracts the first character from the string, the “ O ”. The “ O ” is
added onto the end of the new string, resulting in “ nly 19 shopping days left until
Christmas!O ” and after .3 seconds the scroll() function will be called again. Then
the string will become “ ly 19 shopping days left until Christmas!On ”, and then “ 19
shopping days left until Christmas!Onl ” and so on. Because the substr() method is
being called so rapidly, the effect is a scrolling banner.
The new string, str , created by the two substr() methods will appear in the docu-
ment's title bar. Every time the function is called (i.e., every .3 seconds), the new
string will appear, giving a scrolling effect.
The new string will also appear in the status bar of the window.
The timer is set here within the scroller() function. The first argument is a refer-
ence to a function that will be called, in this case, scroller , and the second argu-
ment is when it will be called, in this case, in 300 milliseconds or .3 seconds
(300/1000). Because the scroller() function calls itself within the timer, it is recur-
sive and will continue to call itself every .3 seconds until the program ends. The
display is shown in Figure 10.21.
<script type="text/javascript">
var today = new Date();
var year=today.getFullYear();
var future = new Date("December 25,"+ year);
var diff = future.getTime() - today.getTime();
// Number of milliseconds
var days =Math.floor(diff / (1000 * 60 * 60 * 24 ));
// Convert to days
var str=
"Only " + days + " shopping days left until Christmas! ";
function startup() {
function scroller(){
str = str.substring(1, str.length) + str.substring(0,1);
Search WWH ::

Custom Search