I use it in many web-based programs.  Let’s have a look on the features.

tablesorter is a jQuery plugin for turning a standard HTML table with THEAD and TBODY tags into a sortable table without page refreshes. tablesorter can successfully parse and sort many types of data including linked data in a cell. It has many useful features including:

• Multi-column sorting
• Parsers for sorting text, URIs, integers, currency, floats, IP addresses, dates (ISO, long and short formats), time.
• Support for ROWSPAN and COLSPAN on TH elements
• Support secondary “hidden” sorting (e.g., maintain alphabetical sort when sorting on other criteria)
• Extensibility via widget system
• Cross-browser: IE 6.0+, FF 2+, Safari 2.0+, Opera 9.0+
• Small code size

So I don’t need to implement SQL based data sorting or php based sorting. I use jQuery tablesorter 2.0.3 to sort data in table without coding.

Let me list some of them here: jQuery, Ext, MooTools, Prototype, YUI.

Remy Sharp has gone through the jQuery and Prototype frameworks, which are probably the two closest to each other, and has done a side by side comparison of the frameworks by showing you how similar things work on both.

The presentation looks into the utility functions, selectors, DOM manipulation, DOM walking, events, Ajax transport, and browser detection.

There is also other posts tell something about:
Mootools beats jQuery and Ext for AIR
jQuery vs. Prototype: OO JavaScript with or without training wheels
3 reasons why I use jQuery

Every element on a web page has certain events which can trigger JavaScript functions. For example, we can use the onClick event of a button element to indicate that a function will run when a user clicks on the button. We define the events in the HTML tags.

Examples of events:

* A mouse click
* A web page or an image loading
* Mousing over a hot spot on the web page
* Selecting an input box in an HTML form
* Submitting an HTML form
* A keystroke

onload and onUnload

The onload and onUnload events are triggered when the user enters or leaves the page.

The onload event is often used to check the visitor’s browser type and browser version, and load the proper version of the web page based on the information.

Both the onload and onUnload events are also often used to deal with cookies that should be set when a user enters or leaves a page. For example, you could have a popup asking for the user’s name upon his first arrival to your page. The name is then stored in a cookie. Next time the visitor arrives at your page, you could have another popup saying something like: “Welcome John Doe!”.

onFocus, onBlur and onChange

The onFocus, onBlur and onChange events are often used in combination with validation of form fields.

Below is an example of how to use the onChange event. The checkEmail() function will be called whenever the user changes the content of the field:

onSubmit

The onSubmit event is used to validate ALL form fields before submitting it.

Below is an example of how to use the onSubmit event. The checkForm() function will be called when the user clicks the submit button in the form. If the field values are not accepted, the submit should be cancelled. The function checkForm() returns either true or false. If it returns true the form will be submitted, otherwise the submit will be cancelled:

onMouseOver and onMouseOut

onMouseOver and onMouseOut are often used to create “animated” buttons.

Below is an example of an onMouseOver event. An alert box appears when an onMouseOver event is detected:

JavaScript Loops

Very often when you write code, you want the same block of code to run over and over again in a row. Instead of adding several almost equal lines in a script we can use loops to perform a task like this.

In JavaScript there are two different kind of loops:

* for – loops through a block of code a specified number of times
* while – loops through a block of code while a specified condition is true

The for Loop

The for loop is used when you know in advance how many times the script should run.

The while loop

The while loop is used when you want the loop to execute and continue executing while the specified condition is true.

The do…while Loop

The do…while loop is a variant of the while loop. This loop will always execute a block of code ONCE, and then it will repeat the loop as long as the specified condition is true. This loop will always be executed at least once, even if the condition is false, because the code is executed before the condition is tested.

The above three loops are used very often while in JavaScript coding. Look at the difference of them carefully.

Alert Box

An alert box is often used if you want to make sure information comes through to the user.

When an alert box pops up, the user will have to click “OK” to proceed.

Syntax:

Confirm Box

A confirm box is often used if you want the user to verify or accept something.

When a confirm box pops up, the user will have to click either “OK” or “Cancel” to proceed.

If the user clicks “OK”, the box returns true. If the user clicks “Cancel”, the box returns false.

Syntax:

Prompt Box

A prompt box is often used if you want the user to input a value before entering a page.

When a prompt box pops up, the user will have to click either “OK” or “Cancel” to proceed after entering an input value.

If the user clicks “OK” the box returns the input value. If the user clicks “Cancel” the box returns null.

Syntax:

It is not big problem.
Now, Javascript 1.5 is work smoothly on IE6.0 and Navigator 6.0.

If you want to know which JavaScript version your browser support, you can download this html file and load it in your browser.

Or you can run it by JavaScript Version Detector
here.

The Code is shown as below.

Note: The Date object will automatically hold the current date and time as its initial value!

In the example below we set a Date object to a specific date (14th January 2010):

And in the following example we set a Date object to be 5 days into the future:

Two common reasons web developers use cookies are

To idetify visitors
You can detect when a user has previously visited your site and customize what that user sees on subsequent visits.

To save transaction state
You can store the status of any lengthy transactions between your site and your visitors’ browsers to safeguard against interruptions.

Here are some limits of cookies:
Where cookies are placed:
The place is fixed, you can check it on your browser’s options.

How large cookie files can be:
4K only.

how many cookies any given Website can place on a user’s hard drive:
20 cookies per site and set an overall total of 300 cookies per browser.

Which sites have access to cookies:
Cookie visibility is configurable.

JavaScript supports the following data types:

Array An ordered collection. For example:

Boolean True/false data type (values of true or false only). For example:

Date Time and date data type. For example:

null A special data type denoting nonexistence. For example:

Null is not the same as 0 (zero)

Number Numerical data type. For example:

String String (text) data type. For example:

Declaring a function

Call a function

Returning a value from a function

The call function above will not get the result without the returning value.