Chapter : JQuery Intro:
What is jQuery?
jQuery is a lightweight, "write less, do more", JavaScript library.
The purpose of jQuery is to make it much easier to use JavaScript on your website.
jQuery takes a lot of common tasks that require many lines of JavaScript code to accomplish, and wraps them into methods that you can call with a single line of code.
jQuery also simplifies a lot of the complicated things from JavaScript, like AJAX calls and DOM manipulation.
The jQuery library contains the following features:
HTML/DOM manipulation
CSS manipulation
HTML event methods
Effects and animations
AJAX
Utilities
Tip: In addition, jQuery has plugins for almost any task out there.
Chapter : JQuery Get Started
Adding jQuery to Your Web Pages
There are several ways to start using jQuery on your web site. You can:
Download the jQuery library from jQuery.com
Include jQuery from a CDN, like Google
Downloading jQuery
There are two versions of jQuery available for downloading:
Production version - this is for your live website because it has been minified and compressed
Development version - this is for testing and development (uncompressed and readable code)
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-1.12.4.min.js"></script>
</head>
Tip: Place the downloaded file in the same directory as the pages where you wish to use it.
Do you wonder why we do not have type="text/javascript" inside the <script> tag?
This is not required in HTML5. JavaScript is the default scripting language in HTML5 and in all modern browsers!
jQuery CDN
If you don't want to download and host jQuery yourself, you can include it from a CDN (Content Delivery Network).
Both Google and Microsoft host jQuery.
To use jQuery from Google or Microsoft, use one of the following:
Google CDN:
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
</head>
Try it Yourself »
Microsoft CDN:
<head>
<script src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.12.4.min.js"></script>
</head>
Try it Yourself »
One big advantage of using the hosted jQuery from Google or Microsoft:
Many users already have downloaded jQuery from Google or Microsoft 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.
Chapter : JQuery Syntax
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()
A $ sign to define/access jQuery
A (selector) to "query (or find)" HTML elements
A jQuery action() to be performed on the element(s)
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".
Are you familiar with CSS selectors?
jQuery uses CSS syntax to select elements. You will learn more about the selector syntax in the next chapter of this tutorial.
The Document Ready Event
You might have noticed that all jQuery methods in our examples, are inside a document ready event:
$(document).ready(function(){
// jQuery methods go here...
});
This is to prevent any jQuery code from running before the document is finished loading (is ready).
It is good practice to wait for the document to be fully loaded and ready before working with it. This also allows you to have your JavaScript code before the body of your document, in the head section.
Here are some examples of actions that can fail if methods are run before the document is fully loaded:
Trying to hide an element that is not created yet
Trying to get the size of an image that is not loaded yet
Tip: The jQuery team has also created an even shorter method for the document ready event:
$(function(){
// jQuery methods go here...
});
Chapter: jQuery Selectors
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: $().
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")
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")
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")
More Examples of jQuery Selectors
Syntax Description Example
$("*") Selects all elements Try it
$(this) Selects the current HTML element Try it
$("p.intro") Selects all <p> elements with class="intro" Try it
$("p:first") Selects the first <p> element Try it
$("ul li:first") Selects the first <li> element of the first <ul> Try it
$("ul li:first-child") Selects the first <li> element of every <ul> Try it
$("[href]") Selects all elements with an href attribute Try it
$("a[target='_blank']") Selects all <a> elements with a target attribute value equal to "_blank" Try it
$("a[target!='_blank']") Selects all <a> elements with a target attribute value NOT equal to "_blank" Try it
$(":button") Selects all <button> elements and <input> elements of type="button" Try it
$("tr:even") Selects all even <tr> elements Try it
$("tr:odd") Selects all odd <tr> elements
jQuery Event Methods
jQuery is tailor-made to respond to events in an HTML page.
What are Events?
All the different visitor's actions that a web page can respond to are called events.
An event represents the precise moment when something happens.
Examples:
moving a mouse over an element
selecting a radio button
clicking on an element
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. This event is already explained in the jQuery Syntax chapter.
click()
The click() method attaches an event handler function to an HTML element.
The function is executed when the user clicks on the HTML element.
The following example says: When a click event fires on a <p> element; hide the current <p> element:
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:
Example
$("p").dblclick(function(){
$(this).hide();
})
mouseenter()
The mouseenter() method attaches an event handler function to an HTML element.
The function is executed when the mouse pointer enters the HTML element:
Example
$("#p1").mouseenter(function(){
alert("You entered p1!");
});
mouseleave()
The mouseleave() method attaches an event handler function to an HTML element.
The function is executed when the mouse pointer leaves the HTML element:
mousedown()
The mousedown() method attaches an event handler function to an HTML element.
The function is executed, when the left, middle or right mouse button is pressed down, while the mouse is over the HTML element:
mouseup()
The mouseup() method attaches an event handler function to an HTML element.
The function is executed, when the left, middle or right mouse button is released, while the mouse is over the HTML element:
hover()
The hover() method takes two functions and is a combination of the mouseenter() and mouseleave() methods.
The first function is executed when the mouse enters the HTML element, and the second function is executed when the mouse leaves the HTML element:
focus()
The focus() method attaches an event handler function to an HTML form field.
The function is executed when the form field gets focus:
blur()
The blur() method attaches an event handler function to an HTML form field.
The function is executed when the form field loses focus:
The on() Method
The on() method attaches one or more event handlers for the selected elements.
Attach a click event to a <p> element:
Chapter: jQuery Hide/Show
jQuery Effects - Hide and Show
Hide, Show, Toggle, Slide, Fade, and Animate. WOW!
Examples
jQuery hide()
Demonstrates a simple jQuery hide() method.
jQuery hide()
Another hide() demonstration. How to hide parts of text.
Syntax:
$(selector).hide(speed,callback);
$(selector).show(speed,callback);
The optional speed parameter specifies the speed of the hiding/showing, and can take the following values: "slow", "fast", or milliseconds.
The optional callback parameter is a function to be executed after the hide() or show() method completes (you will learn more about callback functions in a later chapter).
The following example demonstrates the speed parameter with hide():
Example
$("button").click(function(){
$("p").hide(1000);
});
jQuery toggle()
With jQuery, you can toggle between the hide() and show() methods with the toggle() method.
Shown elements are hidden and hidden elements are shown:
Example
$("button").click(function(){
$("p").toggle();
});
Syntax:
$(selector).toggle(speed,callback);
The optional speed parameter can take the following values: "slow", "fast", or milliseconds.
The optional callback parameter is a function to be executed after toggle() completes.
Chapter: jQuery Fade
jQuery Effects - Fading
With jQuery you can fade elements in and out of visibility.
Examples
jQuery fadeIn()
Demonstrates the jQuery fadeIn() method.
jQuery fadeOut()
Demonstrates the jQuery fadeOut() method.
jQuery fadeToggle()
Demonstrates the jQuery fadeToggle() method.
jQuery fadeTo()
Demonstrates the jQuery fadeTo() method
jQuery Fading Methods
With jQuery you can fade an element in and out of visibility.
jQuery has the following fade methods:
fadeIn()
fadeOut()
fadeToggle()
fadeTo()
jQuery fadeIn() Method
The jQuery fadeIn() method is used to fade in a hidden element.
Syntax:
$(selector).fadeIn(speed,callback);
The optional speed parameter specifies the duration of the effect. It can take the following values: "slow", "fast", or milliseconds.
The optional callback parameter is a function to be executed after the fading completes.
The following example demonstrates the fadeIn() method with different parameters:
Example
$("button").click(function(){
$("#div1").fadeIn();
$("#div2").fadeIn("slow");
$("#div3").fadeIn(3000);
});
jQuery fadeOut() Method
The jQuery fadeOut() method is used to fade out a visible element.
Syntax:
$(selector).fadeOut(speed,callback);
The optional speed parameter specifies the duration of the effect. It can take the following values: "slow", "fast", or milliseconds.
The optional callback parameter is a function to be executed after the fading completes.
The following example demonstrates the fadeOut() method with different parameters:
Example
$("button").click(function(){
$("#div1").fadeOut();
$("#div2").fadeOut("slow");
$("#div3").fadeOut(3000);
});
Try it Yourself »
jQuery fadeToggle() Method
The jQuery fadeToggle() method toggles between the fadeIn() and fadeOut() methods.
If the elements are faded out, fadeToggle() will fade them in.
If the elements are faded in, fadeToggle() will fade them out.
Syntax:
$(selector).fadeToggle(speed,callback);
The optional speed parameter specifies the duration of the effect. It can take the following values: "slow", "fast", or milliseconds.
The optional callback parameter is a function to be executed after the fading completes.
The following example demonstrates the fadeToggle() method with different parameters:
jQuery fadeTo() Method
The jQuery fadeTo() method allows fading to a given opacity (value between 0 and 1).
Syntax:
$(selector).fadeTo(speed,opacity,callback);
The required speed parameter specifies the duration of the effect. It can take the following values: "slow", "fast", or milliseconds.
The required opacity parameter in the fadeTo() method specifies fading to a given opacity (value between 0 and 1).
The optional callback parameter is a function to be executed after the function completes.
The following example demonstrates the fadeTo() method with different parameters:
Chapter: jQuery Slide
jQuery Effects - Sliding
The jQuery slide methods slide elements up and down.
Examples
jQuery slideDown()
Demonstrates the jQuery slideDown() method.
jQuery slideUp()
Demonstrates the jQuery slideUp() method.
jQuery slideToggle()
Demonstrates the jQuery SlideToggle() method.
jQuery Sliding Methods
With jQuery you can create a sliding effect on elements.
jQuery has the following slide methods:
slideDown()
slideUp()
slideToggle()
jQuery slideDown() Method
The jQuery slideDown() method is used to slide down an element.
Syntax:
$(selector).slideDown(speed,callback);
The optional speed parameter specifies the duration of the effect. It can take the following values: "slow", "fast", or milliseconds.
The optional callback parameter is a function to be executed after the sliding completes.
jQuery slideUp() Method
The jQuery slideUp() method is used to slide up an element.
Syntax:
$(selector).slideUp(speed,callback);
The optional speed parameter specifies the duration of the effect. It can take the following values: "slow", "fast", or milliseconds.
The optional callback parameter is a function to be executed after the sliding completes.
jQuery slideToggle() Method
The jQuery slideToggle() method toggles between the slideDown() and slideUp() methods.
If the elements have been slid down, slideToggle() will slide them up.
If the elements have been slid up, slideToggle() will slide them down.
$(selector).slideToggle(speed,callback);
The optional speed parameter can take the following values: "slow", "fast", milliseconds.
The optional callback parameter is a function to be executed after the sliding completes.
The following example demonstrates the slideToggle() method:
Chapter: jQuery Animate
jQuery Effects - Animation
The jQuery animate() method lets you create custom animations.
jQuery Animations - The animate() Method
The jQuery animate() method is used to create custom animations.
Syntax:
$(selector).animate({params},speed,callback);
The required params parameter defines the CSS properties to be animated.
The optional speed parameter specifies the duration of the effect. It can take the following values: "slow", "fast", or milliseconds.
The optional callback parameter is a function to be executed after the animation completes.
The following example demonstrates a simple use of the animate() method; it moves a <div> element to the right, until it has reached a left property of 250px:
jQuery animate() - Manipulate Multiple Properties
Notice that multiple properties can be animated at the same time:
Is it possible to manipulate ALL CSS properties with the animate() method?
Yes, almost! However, there is one important thing to remember: all property names must be camel-cased when used with the animate() method: You will need to write paddingLeft instead of padding-left, marginRight instead of margin-right, and so on.
Also, color animation is not included in the core jQuery library.
If you want to animate color, you need to download the Color Animations plugin from jQuery.com.
jQuery animate() - Using Relative Values
It is also possible to define relative values (the value is then relative to the element's current value). This is done by putting += or -= in front of the value:
Example
$("button").click(function(){
$("div").animate({
left: '250px',
height: '+=150px',
width: '+=150px'
});
});
jQuery animate() - Using Pre-defined Values
You can even specify a property's animation value as "show", "hide", or "toggle":
Example
$("button").click(function(){
$("div").animate({
height: 'toggle'
});
});
jQuery animate() - Uses Queue Functionality
By default, jQuery comes with queue functionality for animations.
This means that if you write multiple animate() calls after each other, jQuery creates an "internal" queue with these method calls. Then it runs the animate calls ONE by ONE.
So, if you want to perform different animations after each other, we take advantage of the queue functionality:
Example 1
$("button").click(function(){
var div = $("div");
div.animate({height: '300px', opacity: '0.4'}, "slow");
div.animate({width: '300px', opacity: '0.8'}, "slow");
div.animate({height: '100px', opacity: '0.4'}, "slow");
div.animate({width: '100px', opacity: '0.8'}, "slow");
});
Chapter: Stop Animations
The jQuery stop() method is used to stop animations or effects before it is finished.
Examples
jQuery stop() sliding
Demonstrates the jQuery stop() method.
jQuery stop() animation (with parameters)
Demonstrates the jQuery stop() method.
jQuery stop() Method
The jQuery stop() method is used to stop an animation or effect before it is finished.
The stop() method works for all jQuery effect functions, including sliding, fading and custom animations.
Syntax:
$(selector).stop(stopAll,goToEnd);
The optional stopAll parameter specifies whether also the animation queue should be cleared or not. Default is false, which means that only the active animation will be stopped, allowing any queued animations to be performed afterwards.
The optional goToEnd parameter specifies whether or not to complete the current animation immediately. Default is false.
So, by default, the stop() method kills the current animation being performed on the selected element.
The following example demonstrates the stop() method, with no parameters:
Example
$("#stop").click(function(){
$("#panel").stop();
});
Chapter: jQuery Callback
jQuery Callback Functions
jQuery Callback Functions
JavaScript statements are executed line by line. However, with effects, the next line of code can be run even though the effect is not finished. This can create errors.
To prevent this, you can create a callback function.
A callback function is executed after the current effect is finished.
Typical syntax: $(selector).hide(speed,callback);
Examples
The example below has a callback parameter that is a function that will be executed after the hide effect is completed:
Example with Callback
$("button").click(function(){
$("p").hide("slow", function(){
alert("The paragraph is now hidden");
});
});
The example below has no callback parameter, and the alert box will be displayed before the hide effect is completed:
Example without Callback
$("button").click(function(){
$("p").hide(1000);
alert("The paragraph is now hidden");
});
Chapter: jQuery Chaining
With jQuery, you can chain together actions/methods.
Chaining allows us to run multiple jQuery methods (on the same element) within a single statement.
jQuery Method Chaining
Until now we have been writing jQuery statements one at a time (one after the other).
However, there is a technique called chaining, that allows us to run multiple jQuery commands, one after the other, on the same element(s).
Tip: This way, browsers do not have to find the same element(s) more than once.
To chain an action, you simply append the action to the previous action.
The following example chains together the css(), slideUp(), and slideDown() methods. The "p1" element first changes to red, then it slides up, and then it slides down:
Example
$("#p1").css("color", "red").slideUp(2000).slideDown(2000);
We could also have added more method calls if needed.
Tip: When chaining, the line of code could become quite long. However, jQuery is not very strict on the syntax; you can format it like you want, including line breaks and indentations.
This also works just fine:
