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jQuery Introduction-

by Alok Swain

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About Me

Why jQuery ?• Makes Javascript coding easier.• Increases the speed of development.• Extensive support through community

forums and large plugin base for numerous features.

• Example:document.getElementbyId(‘myElement’);

$(‘#myElement’)

Main objectives of jQuery• Improving interactions between

JavaScript and HTML.• Highly effective, readable and short

code.• Almost everything converts to find a

certain element and do something on it.

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jQuery Selectors• Basic CSS selectors. Example- .myClass,

#tableID, a.myLink...• Position based selectors: a:first, p:last...• a:hidden • Showcase example

Selectors continued...• Multiple elements can also be selected to

perform a common function on them.e.g. - $(“div#myDiv, #someID”)

DOM Traversal• $(“div.myDiv”).parent();- returns the

immediate parent.• $(“div.myDiv”).next(); - returns the next

sibling.• $(“h1:first”).parents(); - returns all parents

upto the html tag.

DOM Modification.• $(“div#myDiv”).html(“Some Text.”);• $(“table#myTable).append(“<tr> </tr>”);• Showcase example

Chaining method calls.• Most jQuery methods return another jQuery object

representing the same collection.• Thus on the output of one method other methods

calls can be chained. This is one of the powerful features of jQuery.

• Some methods return a different collection.• In such cases .end() method can be used to revert to

the previous collection.• Showcase example:

$('div.section').hide().addClass('gone');

Events• Events can be fired when an element is

clicked, hovered upon, dragged.• Default events associated with certain

elements can also be changed.• Showcase example

Animations• $(“#myDiv”).show(‘slow/fast’);• Showcase Example

Ajax• $.get();• $.post();• $.ajax({

type: ‘get’, url: '/ajax/method/?parameter=' +

param, dataType: 'script' });• Showcase Example

Plugins• Extensive Plugin support for many commonly

desired functionalities.• Defining custom plugins is also possible with

very little effort.• Plugin examples:

1. Tablesorter 2. Facebox

Extending jQuery• jQuery is extensible through plugins, whichcan add new methods to the jQuery object.• UI – Widgets.• Showcase example.

Disadvantages.• Compared to other JavaScript libraries jQuery

has fewer utility functions.• This issue is countered by using other libraries

like Underscore.js which includes many utility functions that Prototype has.

Thank you &

Questions

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