JavaScript Use and Functions

Javascript is structured and interpreted object-oriented language. JavaScript gives you access to the entire Web page. You can modify properties of the page or any element of the page. You can also create new documents or update parts of a form.
JavaScript is designed to be easy to learn and convenient to use by almost anyone who seeks to create dynamic Web pages and client-side checking of input forms.
Moreover, keeping this thing in mind, the authors of JavaScript have provided you, the programmer, with many built-in objects. These built-in objects are available through both the client-side JavaScript and through LiveWire.

Before JavaScript, the process of creating and validating information that a user entered via a form depended heavily on sending and receiving information from a server-side CGI script. A CGI possibly used for creating the actual form, validating the information and sending a response back to the user confirming that the information sent successfully.
Moreover, now by using JavaScript, you can place much of the work on the client-side, which can reduce the connection times between the client and the server dramatically. Regarding validating form information, you do this by allowing the script to inspect the contents of each field that the user has entered and presented an alert to the user if the information does not meet some specific requirements like too many characters or if the field is empty.
Although Javascript does not force you to declare or initialize variables before you begin function statements, it is often very useful to do so.It allows you to document the purpose of each variable.
When you return to a function six months after you wrote it, you may not remember what the variable count does, unless you explicitly document it as // array index variable.However, if you explicitly declare each variable, then you have the opportunity to initialize them to some significant default value.

Functions, particularly ones that carry out critical tasks like opening windows, should always check to see if their parameters are valid. It usually involves making sure that they are the correct type and are within some expected range.Then, we need routines to determine if the parameters are valid. Strings are relatively safe as parameters, but numbers and booleans are not.
It is because JavaScript often converts a non-string, such as 5, to the corresponding string "5," but it only converts to numerical or boolean values if it can. If a string parameter is specified as the number 5, no error occurs, because the numerical value 5 and the string "5" may freely convert to one another. If a statistical parameter specified as the string "Five," an error very definitely occurs, because JavaScript does not know how to convert that string to a number.

Detect Visitor's Browser

<script type="text/javascript">
var ie7 = (document.all && !window.opera && window.XMLHttpRequest) ? true : false;
if (ie7==true)
document.write( "Is IE7" );
document.write( "Is NOT IE7" );
Using object detection
Object detection is more reliable than browser detection.
Object detection means checking for the existence of a method or property rather than checking for the browser.
However, in object detection, you check for the availability of XMLHttpRequest, and if it is available we create an object of it, else we try for the other.
"if(window.XMLHttpRequest) {
req = new XMLHttpRequest();
req = new ActiveXObject('MSXML2.XMLHTTP');
try {
    req = new ActiveXObject('Microsoft.XMLHTTP');
    return false;
Set Cursor to Empty Field in Login Form
"if (document.yourform.fieldname.value == "") {
alert("You have not filledin this field.");
if(document.all || document.getElementByID){ = "pink";
return false;
use this
JavaScript onChange function

The onChange javascript function for selectBox supported by both Internet Explorer and Mozilla Firebox
<select name="selectedPartNumber" onchange="javascript:goSelected(a);">
Redirect Using JavaScript
<script language="javascript">
function CountDown( )
var current = document.getElementById('CountDown').innerHTML;
var next = current – 1;
document.getElementById('CountDown').innerHTML = next ;
if( next == 0 )
window.location.href = ';;
setTimeout( "CountDown()", 1000 );

<body onload="CountDown( );">
Redirecting in <span id="CountDown">5</span>
Displaying Picture Dynamically

Display a pattern ID (text) directly above or under the picture.
1. Get a "pointer" to the HTML element you want to change (let's say it is a div)
2. You set the innerHTML to the new value.
"<div id="PatternID"> 111 </div>
var obj = document.getElementById("PatternID");
if (obj != null)
obj.innerHTML = "222";"



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I'm Communication Director with SCPL. Our goal is to deliver the most accurate information possible based on the needs of the majority of website owners and developers, and Ananova reports deliver the most reliable indicators of web host performance. -

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