JQUERY
PREPARED BY
SONIA MAHINDRU
ASSISTANT PROFESSOR IN COMPUTER SCIENCE
HANSRAJ MAHILA MAHA VIDYALAYA JALANDHAR
jQuery Introduction
The jQuery library contains the following features:
HTML/DOM manipulation
CSS manipulation
HTML event methods
Effects and animations
AJAX
Utilities
There are lots of other JavaScript libraries out there, but jQuery is probably the most popular, and also the most extendable.
Many of the biggest companies on the Web use jQuery, such as:
Google, Microsoft, IBM, Netflix
The jQuery team knows all about cross-browser issues, and they have written this knowledge into the jQuery library. jQuery will run exactly the same in all major browsers.
Adding jQuery to Your Web Pages
There are several ways to start using jQuery on your web site. You can:
Downloading jQuery
There are two versions of jQuery available for downloading:
Both versions can be downloaded from jQuery.com.
The jQuery library is a single JavaScript file, and you reference it with the HTML <script> tag (notice that the <script> tag should be inside the <head> section):
<head>�<script src="jquery-3.5.1.min.js"></script>�</head>
Place the downloaded file in the same directory as the pages where you wish to use it.
jQuery CDN
If you don't want to download and host jQuery yourself, you can include it from a CDN (Content Delivery Network).
Google is an example of someone who host jQuery:
Google CDN:
<head>�<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>�</head
One big advantage of using the hosted jQuery from Google:��Many users already have downloaded jQuery from Google when visiting another site. As a result, it will be loaded from cache when they visit your site, which leads to faster loading time. Also, most CDN's will make sure that once a user requests a file from it, it will be served from the server closest to them, which also leads to faster loading time.
With jQuery you select (query) HTML elements and perform "actions" on them.
jQuery Syntax
The jQuery syntax is tailor-made for selecting HTML elements and performing some action on the element(s).
Basic syntax is: $(selector).action()
Examples:
$(this).hide() - hides the current element.
$("p").hide() - hides all <p> elements.
$(".test").hide() - hides all elements with class="test".
$("#test").hide() - hides the element with id="test".
��jQuery uses CSS syntax to select elements
jQuery Selectors
jQuery selectors allow you to select and manipulate HTML element(s).
jQuery selectors are used to "find" (or select) HTML elements based on their name, id, classes, types, attributes, values of attributes and much more. It's based on the existing CSS Selectors, and in addition, it has some own custom selectors.
All selectors in jQuery start with the dollar sign and parentheses: $().
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The element Selector
The jQuery element selector selects elements based on the element name.
You can select all <p> elements on a page like this:
$("p")
Example
When a user clicks on a button, all <p> elements will be hidden:
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
$("button").click(function(){
$("p").hide();
});
});
</script>
</head>
<body>
<h2>This is a heading</h2>
<p>This is a paragraph.</p>
<p>This is another paragraph.</p>
<button>Click me to hide paragraphs</button>
</body>
</html>
The #id Selector
The jQuery #id selector uses the id attribute of an HTML tag to find the specific element.
An id should be unique within a page, so you should use the #id selector when you want to find a single, unique element.
To find an element with a specific id, write a hash character, followed by the id of the HTML element:
$("#test")
Example
When a user clicks on a button, the element with id="test" will be hidden:
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
$("button").click(function(){
$("#test").hide();
});
});
</script>
</head>
<body>
<h2>This is a heading</h2>
<p>This is a paragraph.</p>
<p id="test">This is another paragraph.</p>
<button>Click me</button>
</body>
</html>
The .class Selector
The jQuery .class selector finds elements with a specific class.
To find elements with a specific class, write a period character, followed by the name of the class:
$(".test")
Example
When a user clicks on a button, the elements with class="test" will be hidden:
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
$("button").click(function(){
$(".test").hide();
});
});
</script>
</head>
<body>
<h2 class="test">This is a heading</h2>
<p class="test">This is a paragraph.</p>
<p>This is another paragraph.</p>
<button>Click me</button>
</body>
</html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
$("button").click(function(){
$("ul li:first").hide();
});
});
</script>
</head>
<body>
<p>List 1:</p>
<ul>
<li>Coffee</li>
<li>Milk</li>
<li>Tea</li>
</ul>
<p>List 2:</p>
<ul>
<li>Coffee</li>
<li>Milk</li>
<li>Tea</li>
</ul>
<button>Click me</button>
</body>
</html>
jQuery Event Methods
jQuery is tailor-made to respond to events in an HTML page.
What are Events?
All the different visitors' actions that a web page can respond to are called events.
An event represents the precise moment when something happens.
Examples:
The term "fires/fired" is often used with events. Example: "The keypress event is fired, the moment you press a key".
Here are some common DOM events:
Mouse Events | Keyboard Events | Form Events | Document/Window Events |
click | keypress | submit | load |
dblclick | keydown | change | resize |
mouseenter | keyup | focus | scroll |
mouseleave |
| blur | unload |
jQuery Syntax For Event Methods
In jQuery, most DOM events have an equivalent jQuery method.
To assign a click event to all paragraphs on a page, you can do this:
$("p").click();
The next step is to define what should happen when the event fires. You must pass a function to the event:
$("p").click(function()
{� // action goes here!!�});
Commonly Used jQuery Event Methods
$(document).ready()
The $(document).ready() method allows us to execute a function when the document is fully loaded.
dblclick()
The dblclick() method attaches an event handler function to an HTML element.
The function is executed when the user double-clicks on the HTML element:
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script>
$(document).ready(function()
{
$("p").dblclick(function(){
$(this).hide();
});
});
</script>
</head>
<body>
<p>If you double-click on me, I will disappear.</p>
<p>Click me away!</p>
<p>Click me too!</p>
</body>
</html>
THANK YOU