Handling Events In JQuery

Handling Events using JavaScript

Question :What type of JavaScript code do you write to handle a button click event?

Answer

It depends on the browser!

Event Attachment Techniques

Most Browsers

mybutton.addEventListerer(‘click’,function() {}, false);

Internet Explorer

mybutton.attachment(‘onclick’,function() { });

jQuery Event Model Benefits

Events notify a program that a user performed some type of action

jQuery provides a cross-browser event model that works in IE, Chrome, Opera, Firefox, Safari and more

jQuery event model is simple to use and provides a compact syntax

<html>

<head>

</head>

<body>

<button id=”buttonId”> click</button>

var myButton=document.getElementById(“buttonId”);

if(document.addEventListener) {

myButton.addEventListener(“click”,function()) {alert(“click Button”);},false);

}else{

mybutton.attachEvent(“onclick”,function(){alert(“click IE Button”);});

}

</script>

</body>

</html>

Handling Click Events

Raising a click event from within another function:

$(‘#otherID’).click(function() {

$(‘#myID’).click();

});

This would fire when the element otherID was clicked and raise the click event for myID

<html>

<head>

$(document).ready(function() {

$(‘#buttonid1’).click(function() {

// raising the event using jQuery function

alert(“button1 is clicked”);

$(“#buttonld2”).click();

});

$(“#buttonid2”).click(function() {

alert(“button2 is clicked”);

});

</script>

</head>

<body>

<button id=”buttonid1”> click</button>

<button id=”buttonid2”> click2</button>

</body>

</html>

<html>

<head>

$(document).ready(function() {

alert(“City Dropdown changed to :” + $(this).val());

});

</script>

</head>

<body>

<option value=”hyd”>Hyderabad</option>

<option value=”bang”>Banglore</option>

<option value=”mumbai”>Mumbai</option>

<option value=”hyd”>Hyderabad</option>

</select>

</body>

</html>

Handling Click Events

click(handler(eventObject)) is used to listen for a click event or trigger a click event on an element

$(‘#myID’).click(function() {

alert(‘The element myID was clicked’);

});

<html>

<head>

.Hilight:

bigground-color:pink;

}

</style>

$(document).ready(function(){

$(“div#myDiv”).click(function(event) {

$(this).addClass(“Hilight”);

var result=””;

result=result+”x:”+event.pageX+”<br/>”;

result=result+”Y:”+event.pageY+”<br/>”;

result=result+”keycode:”+event.keycode+”<br/>”;

result=result+”TimeStamp:” + event.timeStamp+”<br/>”;

result=result+”Target element ID:”+$(event.target).attr(“id”)+”<br/>”;

result=result+”Event type:” + event.type+”<br/>”;

$(this).html(result);

});

</sript>

</head>

<body>

This is my div

</div>

</body>

</html>

<html>

<head>

.Hilight:

bigground-color:pink;

}

</style>

$(document).ready(function(){

$(“div#myDiv”).mouseenter(function() {

$(this).toggleclass(“Hilight”);

}).mouseleave(function(){

$(this).toggleclass(“Hilight”);

}}.click(function(event){

$(this).text(“X: “+event.pageX+”Y:”+event.pageY);

}};

</sript>

</head>

<body>

This is my div

</div>

</body>

</html>

Using bind()

.bind(eventType,handler(eventObject)) attaches a handler to an event for the selected element(s)

$(‘#MyDiv’).bind(‘click’,function()) {

//Handle click event

});

.click() is the same as .bind(‘click’)

Using unbind()

unbind(event) is used to remove a handler previously bound to an element:

$(‘#test’).click(handler); can be unbound using

$(‘#text’).unbind();

Specific events can also be targeted using unbind():

$(‘#test’).unbind(‘click’);

Binding Multiple Events using jQuery

bind() allows multiple events to be bound to one or more elements

Event names to bind are separated with a space:

$(‘#MyDiv’).bind(‘mouseenter mouseleave’,

function()

{

$(this).toggleclass(‘entered’);

}

);

<html>

<head>

.Hilight:

bigground-color:pink;

}

</style>

$(document).ready(function(){

$(“div#myDiv”).bind(“mouseenter mouseleave click”,function(event) {

$(this).toggleClass(“Hilight”);

if(envetscope==’click’){

$(this).add(“X:” + even.pageX+”Y:”+event.pageY);

}

});

$(“button”).click function(){

//$(“divmyDiv”).unbind();

$(“div#.Div”).unbind(“click”);

}};

});

</sript>

</head>

<body>

This is my div

</div>

<button>Unbind even button</button>

</body>

</html>

live() and delegate() Functions

live() and delegate() allow new elements added into the DOM automatically be “attached” to an event handler

live() – Allow binding of event handlers to elements that match selector, including future elements. Events bubble upto the document object.

delegate() – Replacement for live() in jQuery 1.4

Attaches an event handler directly to the selector context.

Using live()

Event handlers can be set using live()

The document object handles events by default

Works even when new objects are added into the DOM:

$(‘.someclass’).live(‘click’,someFunction);

Stop live event handling using die();

$(‘.someClass’).die(‘click’,someFunction);

Screenshot_10

Click Event

<spanclass=”someclass”/>

Using delegate()

Newer version of live() added in jQuery 1.4

A context object (#Divs in the sample belpw) handles events by default rather than the document object

Works even when new objects are added into the DOM:

$(‘#Divs’).delegate(‘div’,’click’,someFunction);

Stop delegate event handling using undelegate()

How delegate() works

Screenshot_11

Click Event

<html>

<head>

$(document).ready(function(){

var PhoneDiv=$(“div#newDiv”);

$(“#AddPhoneButton”,click(function(){

var phoneType.Clone=$(“div:eq(0)”.PhoneDiv).clone();

var PhoneNumber.Divclone=$(“div:eq(1)”,PhoneDiv).clone();

$(“select”,phone.typeDivclone).val(“);

$(“input”,phone.NumberDivclone).val(‘’)l

PhoneDiv.apper(“<div style=’clear:both’/>”.append(PhoneTypeDivcloappend(PhoneNumberDivclone)));

$(“input”,PhoneDiv).keypress”,function(event){

if(event.keycode(48) || event.keycode>57){

//even propagation();

return;

}

}};

$(“button”).click(function) {

// $(“input”,phoneDiv).die();

$(“input”,Phonediv).die(“keypress”);

});

PhoneDiv.delegate(“im”,”keypress”,function(event){

if(event.keycode 48 || event.keycode>57){

//even popPropagatation();

return;

}

}0;

$(“button”).click(function){

PhoneDiv.undelegate(“input”,”keypress”);

}};

</script>

</head>

<body>

<tr>

<td>

</td>

</tr>

<tr>

<td> Password </td>

<td>

</td>

</tr>

<tr>

<td> Address</td>

<td>

</td>

</tr>

<tr>

<td>Phone</td>

<td>

<option value=””>Select One</option>

<option value=”Mobile”>Mobile</option>

<option value=”Office”>Office</option>

</select>

</div>

</div>

</td>

</tr>

<tr>

<td>

<option value=”hyd”>Hyderabad</option>

<option value=”bang”>Banglore</option>

<option value=”chennai”>chennai</option>

<option value=”mumbai”>Mumbai</option>

</select>

</td>

</tr>

<tr>

</td>

</tr>

</table>

<button>Release Event Handlers</button>

</body>

</html>