Now that all of the pieces have been explained, look at the entire source code below to see how to put it all together:
<HTML>
<HEAD>
<TITLE>Shudder</TITLE>
<STYLE TYPE="text/css">
<!—
#Central {position:absolute; left:0; top:0; width:575; height:300; z-index:2; visibility:hidden;}
#Behind {position:absolute; left:0; top:0; width:575; height:300; z-index:1; visibility:hidden;}
//-->
</STYLE>
<SCRIPT LANGUAGE="JavaScript">
<!--
function browser_Sniff() {
//Determines which browser and version is being used
var agent = navigator.userAgent.toLowerCase();
this.major = parseInt(navigator.appVersion);
this.minor = parseFloat(navigator.appVersion);
this.ns = ((agent.indexOf('mozilla')!=-1) &&
((agent.indexOf('spoofer')==-1) &&
(agent.indexOf('compatible') == -1)));
this.ns2 = (this.ns && (this.major == 3));
this.ns3 = (this.ns && (this.major == 3));
this.ns4b = (this.ns && (this.minor < 4.04));
this.ns4 = (this.ns && (this.major >= 4));
this.ie = (agent.indexOf("msie") != -1);
this.ie3 = (this.ie && (this.major == 2));
this.ie4 = (this.ie && (this.major >= 4));
this.op3 = (agent.indexOf("opera") != -1);
this.win = (agent.indexOf("win")!=-1);
this.mac = (agent.indexOf("mac")!=-1);
this.unix = (agent.indexOf("x11")!=-1);
}
// VARIABLES
var is = new browser_Sniff(); // Calls Browser sniffing function
function standardize() {
// Once browser has been sniffed
// these conditionals set Netscape and Microsoft syntax
// to the same variable, so that only one function need be written
if(is.ns4) {
doc = "document";
sty = "";
htm = ".document"; }
else if(is.ie4) {
doc = "document.all";
sty = ".style";
htm = ""; }
}
// Sets variables for image manipulation
var bool = 1;
function Load_Name() { //Creates layer objects
Centralobj = eval(doc + '["Central"]' + sty);
Behindobj = eval(doc + '["Behind"]' + sty);
}
function Position() {
Centralobj.left = (available_width / 2) - 211;
Centralobj.top = (available_height / 2) - 143;
Centralobj.visibility = 'visible';
Behindobj.left = (available_width / 2) - 211;
Behindobj.top = (available_height / 2) - 143;
Behindobj.visibility = 'visible';
}
function Shudder() {
var x = Math.random();
var y = Math.random();
Behindobj.top = (available_height / 2) - (145 * y) - (Math.cos(x *10) + (x * y));
Behindobj.left = (available_width / 2) - (100 * x) - (Math.sin(y *10) + (2 * y * x));
}
// -->
</script>
</HEAD>
<BODY BGCOLOR="BLACK" MARGINWIDTH="0" MARGINHEIGHT="0" SCROLL="NO" onLoad="
if(is.ns4) {
available_width=innerWidth;
available_height=innerHeight;
}
else if(is.ie4) {
available_width=document.body.clientWidth;
available_height=document.body.clientHeight;
};
standardize(); Load_Name(); setTimeout('Position()',.01);">
<DIV ID="Central"><IMG SRC="graphics/sundunes.jpg" width="422" height="286" onmousemove="Shudder()"></DIV>
<DIV ID="Behind"><IMG SRC="graphics/sundunes_b.jpg"></DIV>
</BODY>
</HTML>
The Shudder effect is just one example of how to use DHTML for special effects on your web page. Now that you have some basics, hopefully you will discover places where you can use DHTML effects to add some spice. To end with a cliché older than JavaScript rollovers, "the possibilities are endless."
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