JQUERY - EVENTS HANDLING

We have the ability to create dynamic web pages by using events. Events are actions that can be detected by your Web Application.

Following are the examples events:

• A mouse click
• A web page loading
• Taking mouse over an element
• Submitting an HTML form
• A keystroke on your keyboard, etc.

When these events are triggered, you can then use a custom function to do pretty much whatever you want with the event. These custom functions call Event Handlers.

Binding Event Handlers

Using the jQuery Event Model, we can establish event handlers on DOM elements with the bind() method as follows:


This code will cause the division element to respond to the click event; when a user clicks inside this division thereafter, the alert will be shown.

This will produce the following result:


The full syntax of the bind() command is as follows:


Following is the description of the parameters:

• eventType: A string containing a JavaScript event type, such as click or submit. Refer to the next section for a complete list of event types.
• eventData: This optional parameter is a map of data that will be passed to the event handler.
• handler: A function to execute each time the event is triggered.

Removing Event Handlers

Typically, once an event handler is established, it remains in effect for the remainder of the life of the page. There may be a need when you would like to remove event handler. jQuery provides the unbind() command to remove an exiting event handler. The syntax of unbind() is as follows:


Following is the description of the parameters:

• eventType: A string containing a JavaScript event type, such as click or submit. Refer to the next section for a complete list of event types.
• handler: If provided, identifies the specific listener that’s to be removed.

Event Types

The following are cross platform and recommended event types which you can bind using JQuery:

S.NO.	Event Type & Description
1	blur Occurs when the element loses focus.
2	change Occurs when the element changes.
3	click Occurs when a mouse click.
4	dblclick Occurs when a mouse double-click.
5	Error Occurs when there is an error in loading or unloading etc.
6	Focus Occurs when the element gets focus.
7	keydown Occurs when key is pressed.
8	keypress Occurs when key is pressed and released.
9	keyup Occurs when key is released.
10	Load Occurs when document is loaded.
11	mousedown Occurs when mouse button is pressed.
12	mouseenter Occurs when mouse enters in an element region.
13	mouseleave Occurs when mouse leaves an element region.
14	Mousemove Occurs when mouse pointer moves.
15	Mouseout Occurs when mouse pointer moves out of an element.
16	Mouseover Occurs when mouse pointer moves over an element.
17	Mouseup Occurs when mouse button is released.
18	Resize Occurs when window is resized.
19	Scroll Occurs when window is scrolled.
20	Select Occurs when a text is selected.
21	Submit Occurs when form is submitted.
22	Unload Occurs when documents is unloaded.

The Event Object

The callback function takes a single parameter; when the handler is called the JavaScript event object will be passed through it.

The event object is often unnecessary and the parameter is omitted, as sufficient context is usually available when the handler is bound to know exactly what needs to be done when the handler is triggered, however there are certain attributes which you would need to be accessed.

The Event Attributes

The following event properties/attributes are available and safe to access in a platform independent manner:

S. NO.	Property & Description
1	altKey Set to true if the Alt key was pressed when the event was triggered, false if not. The Alt key is labeled Option on most Mac keyboards.
2	ctrlKey Set to true if the Ctrl key was pressed when the event was triggered, false if not.
3	data The value, if any, passed as the second parameter to the bind() command when the handler was established.
4	keyCode For keyup and keydown events, this returns the key that was pressed.
5	metaKey Set to true if the Meta key was pressed when the event was triggered, false if not. The Meta key is the Ctrl key on PCs and the Command key on Macs.
6	pageX For mouse events, specifies the horizontal coordinate of the event relative from the page origin.
7	pageY For mouse events, specifies the vertical coordinate of the event relative from the page origin.
8	relatedTarget For some mouse events, identifies the element that the cursor left or entered when the event was triggered.
9	screenX For mouse events, specifies the horizontal coordinate of the event relative from the screen origin.
10	screenY For mouse events, specifies the vertical coordinate of the event relative from the screen origin.
11	shiftKey Set to true if the Shift key was pressed when the event was triggered, false if not.
12	target Identifies the element for which the event was triggered.
13	Timestamp The timestamp (in milliseconds) when the event was created.
14	type For all events, specifies the type of event that was triggered (for example, click).
15	which For keyboard events, specifies the numeric code for the key that caused the event, and for mouse events, specifies which button was pressed (1 for left, 2 for middle, 3 for right).

This will produce the following result:


The Event Methods

There is a list of methods which can be called on an Event Object:

SQL	SQL	SQL Lite
1	preventDefault()	Prevents the browser from executing the default action.
2	isDefaultPrevented()	Returns whether event.preventDefault() was ever called on this event object.
3	stopPropagation()	Stops the bubbling of an event to parent elements, preventing any parent handlers from being notified of the event.
4	isPropagationStopped()	Returns whether event.stopPropagation() was ever called on this event object.
5	stopImmediatePropagation()	Stops the rest of the handlers from being executed.
6	isImmediatePropagationStopped()	Returns whether event.stopImmediatePropagation() was ever called on this event object.

preventDefault() Method

The preventDefault() method prevents the browser from executing the default action.

You can use the method isDefaultPrevented to know whether this method was ever called (on that event object).

Syntax

Here is the simple syntax to use this method:


Parameters

Here is the description of all the parameters used by this method:

• NA

Example

Following is a simple example showing the usage of this method. This example demonstrate how you can stop the browser from changing the page to the href of any anchors.


This will produce the following result:


isDefaultPrevented() Method

The isDefaultPrevented() method checks whether event.preventDefault() was ever called on this event object.

This method returns true in case preventDefault() has been called otherwise it returns false.

Syntax

Here is the simple syntax to use this method:


Parameters

Here is the description of all the parameters used by this method:

• NA

Example

Following is a simple example showing the usage of this method. This example demonstrate how you can stop the browser from changing the page to the href of any anchors.


This will produce the following result:


stopPropagation() Method

The stopPropagation() method stops the bubbling of an event to parent elements, preventing any parent handlers from being notified of the event.

You can use the method event.isPropagationStopped() to know whether this method was ever called (on that event object).

Syntax

Here is the simple syntax to use this method:


Parameters

Here is the description of all the parameters used by this method:

• NA

Example

Following is a simple example showing the usage of this method. This example demonstrate how you can prevent other event handlers from being called:


This will produce the following result:


isPropagationStopped() Method

The isPropagationStopped() method checks whether event.stopPropagation() was ever called on this event object.

This method returns true in case event.stopPropagation() method has been already called, otherwise it returns false.

Syntax

Here is the simple syntax to use this method:


Parameters

Here is the description of all the parameters used by this method:

• NA

Example

Following is a simple example showing the usage of this method:


This will produce the following result:


stopImmediatePropagation() Method

The stopImmediatePropagation() method stops the rest of the handlers from being executed. This method also stops the bubbling by calling event.stopPropagation(). You can use event.isImmediatePropagationStopped() to know whether this method was ever called (on that event object).

Syntax

Here is the simple syntax to use this method:


Parameters

Here is the description of all the parameters used by this method:

• NA

Example

Following is a simple example showing the usage of this method:


This will produce the following result:


isImmediatePropagationStopped() Method

The isImmediatePropagationStopped() method checks whether event.stopImmediatePropagation() was ever called on this event object. This method returns true in case event.stopImmediatePropagation() method has already been called, otherwise it returns false:

Syntax

Here is the simple syntax to use this method:


Parameters

Here is the description of all the parameters used by this method:

• NA

Example

Following is a simple example showing the usage of this method:


This will produce the following result:


Event Manipulation Methods

Following table lists down important event-related methods:

S.No.	Method & Description
1	bind( type, [data], fn ) Binds a handler to one or more events (like click) for each matched element. Can also bind custom events.
2	off( events [, selector ] [, handler(eventObject) ] ) This does the opposite of live, it removes a bound live event.
3	hover( over, out ) Simulates hovering for example moving the mouse on, and off, an object.
4	on( events [, selector ] [, data ], handler ) Binds a handler to an event (like click) for all current − and future − matched element. Can also bind custom events.
5	one( type, [data], fn ) Binds a handler to one or more events to be executed once for each matched element.
6	ready( fn ) Binds a function to be executed whenever the DOM is ready to be traversed and manipulated.
7	trigger( event, [data] ) Trigger an event on every matched element.
8	triggerHandler( event, [data] ) Triggers all bound event handlers on an element.
9	unbind( [type], [fn] ) This does the opposite of bind, it removes bound events from each of the matched elements.

bind( type, [data], fn ) Method

The bind( type, [data], fn ) method binds a handler to one or more events (like click) for each matched element. Can also bind custom events.

Possible event values: blur, focus, load, resize, scroll, unload, click etc.

Syntax

Here is the simple syntax to use this method:


Parameters

Here is the description of all the parameters used by this method:

• type: One or more event types separated by a space.
• data: This is optional paramter and represents additional data passed to the event handler as event.data.
• fn: A function to bind to the event on each of the set of matched elements.

Example

Following is a simple example showing the usage of this method. Here it binds click event with each <div> element:


This will produce the following result:

off( events [, selector ] [, handler(eventObject) ] ) Method

The off( events [, selector ] [, handler(eventObject) ] ) method does the opposite of on() method, it removes a bound live event.

Syntax

Here is the simple syntax to use this method −


Parameter

Here is the description of all the parameters used by this method −

• events − Event types separated by spaces.
• selector − A Selector String
• handler − A function to bind to the event on each of the set of matched elements

Example

Following is a simple example showing the usage of this method.


This will produce the following result:


hover( over, out ) Method

The hover( over, out ) method simulates hovering (moving the mouse on, and off, an object). This is a custom method which provides an 'in' to a frequent task.

Syntax

Here is the simple syntax to use this method:


Parameters

Here is the description of all the parameters used by this method:

• over: The callback function to fire when the mouse is moved over a matched element.
• out: The callback function to fire when the mouse is moved off of a matched element.

Example

Following is a simple example showing the usage of this method:





on( events [, selector ] [, data ], handler ) Method

The on( events [, selector ] [, data ], handler ) method binds a handler to an event (like click) for all current − and future − matched element. Can also bind custom events. Possible event values − blur, focus, load, resize, scroll, unload, click etc.

Syntax

Here is the simple syntax to use this method −


Parameter

Here is the description of all the parameters used by this method −

• events − Event types separated by spaces.
• selector − A Selector String
• data − Data to be passed to the event handler in event.data
• handler − A function to bind to the event on each of the set of matched elements

Example

Following is a simple example showing the usage of this method. Here it binds click event with each <div> element −


This will produce the following result:


one( type, [data], fn ) Method

The one( type, [data], fn ) method binds a handler to one or more events to be executed once for each matched element. The handler is executed only once for each element. Otherwise, the same rules as described in bind() apply.

Possible event values: blur, focus, load, resize, scroll, unload, click etc.

Syntax

Here is the simple syntax to use this method:


Parameters

Here is the description of all the parameters used by this method:

• type: An event type.
• data: This is optional paramter and represents additional data passed to the event handler as event.data.
• fn: A function to bind to the event on each of the set of matched elements.

Example

Following is a simple example showing the usage of this method. Here it binds click event with each <div> element. Try to click any square two times, it won't react unlike bind() method:


This will produce the following result:


ready( fn ) Method

The ready( fn ) method binds a function to be executed whenever the DOM is ready to be traversed and manipulated. This method is a replacement for using window.onload

Syntax

Here is the simple syntax to use this method:


Parameters

Here is the description of all the parameters used by this method:

• fn: The function to be executed when the DOM is ready.

Example

Following is a simple example showing the usage of this method:


This will produce the following result:

trigger( event, [data] ) Method

The trigger( event, [data] ) method triggers an event on every matched element.

Triggered events aren't limited to browser-based events, you can also trigger custom events registered with bind.

Syntax

Here is the simple syntax to use this method:


Parameters

Here is the description of all the parameters used by this method:

• event: An event object or type to trigger.
• data : This is an optional parameters and represents additional data to pass as arguments (after the event object) to the event handler.

Example

Following is a simple example showing the usage of this method. Here you would trigger a click event on square TWO by clicking on square ONE:


This will produce the following result:


triggerHandler( event, [data] ) Method

The triggerHandler( event, [data] ) method triggers all bound event handlers on an element (for a specific event type) WITHOUT executing the browser's default actions, bubbling, or live events.

This method behaves very similarly to the trigger method, with two major exceptions:

• First: No default browser actions are triggered, the triggered event does not bubble, and live events aren't triggered.
• Second: The event is only triggered on the first element within the jQuery collection.

This method returns the return value of the triggered handler instead of a chainable jQuery object.

Syntax

Here is the simple syntax to use this method:


Parameters

Here is the description of all the parameters used by this method:

• event: An event object or type to trigger.
• data : This is an optional parameters and represents additional data to pass as arguments (after the event object) to the event handler.

Example

Following is a simple example showing the usage of this method:


This will produce the following result:

Click on any square below to see the result:


unbind( [type], [fn] ) Method

The unbind( [type], [fn] ) method does the opposite of bind, it removes bound events from each of the matched elements.

Syntax

Here is the simple syntax to use this method:


Parameters

Here is the description of all the parameters used by this method:

• type: One or more event types separated by a space.
• fn: A function to unbind from the event on each of the set of matched elements.

Example

Following is a simple example showing the usage of this method:


This will produce the following result:

Click on any square below to see the result:


Event Helper Methods

jQuery also provides a set of event helper functions which can be used either to trigger an event to bind any event types mentioned above.

Trigger Methods

Following is an example which would triggers the blur event on all paragraphs:


Binding Methods

Following is an example which would bind a click event on all the <div>:


Here is a complete list of all the support methods provided by jQuery:

S.No.	Method & Description
1	blur( ) Triggers the blur event of each matched element.
2	blur( fn ) Bind a function to the blur event of each matched element.
3	change( ) Triggers the change event of each matched element.
4	change( fn ) Binds a function to the change event of each matched element.
5	click( ) Triggers the click event of each matched element.
6	click( fn ) Binds a function to the click event of each matched element.
7	dblclick( ) Triggers the dblclick event of each matched element.
8	dblclick( fn ) Binds a function to the dblclick event of each matched element.
9	error( ) Triggers the error event of each matched element.
10	error( fn ) Binds a function to the error event of each matched element.
11	focus( ) Triggers the focus event of each matched element.
12	focus( fn ) Binds a function to the focus event of each matched element.
13	keydown( ) Triggers the keydown event of each matched element.
14	keydown( fn ) Bind a function to the keydown event of each matched element.
15	keypress( ) Triggers the keypress event of each matched element.
16	keypress( fn ) Binds a function to the keypress event of each matched element.
17	keyup( ) Triggers the keyup event of each matched element.
18	keyup( fn ) Bind a function to the keyup event of each matched element.
19	load( fn ) Binds a function to the load event of each matched element.
20	mousedown( fn ) Binds a function to the mousedown event of each matched element.
21	mouseenter( fn ) Bind a function to the mouseenter event of each matched element.
22	mouseleave( fn ) Bind a function to the mouseleave event of each matched element.
23	mousemove( fn ) Bind a function to the mousemove event of each matched element.
24	mouseout( fn ) Bind a function to the mouseout event of each matched element.
25	mouseover( fn ) Bind a function to the mouseover event of each matched element.
26	mouseup( fn ) Bind a function to the mouseup event of each matched element.
27	resize( fn ) Bind a function to the resize event of each matched element.
28	scroll( fn ) Bind a function to the scroll event of each matched element.
39	select( ) Trigger the select event of each matched element.
30	select( fn ) Bind a function to the select event of each matched element.
31	submit( ) Trigger the submit event of each matched element.
32	submit( fn ) Bind a function to the submit event of each matched element.
33	unload( fn ) Binds a function to the unload event of each matched element.

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