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Handling Events in jQuery

06 October, 2020

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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() { });  

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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>

<script type=”text/javascript” src=”jQuery.js”>

</script>

</head>

<body>

<button id=”buttonId”>

click</button>

<script type=”text/javascript”>

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>

<script type=”text/javascript” src=”jQuery.js”>

</script>

$(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>

<script type=”text/javascript” src=”jQuery.js”></script> <script type=”text/javascript”>

$(document).ready(function()

{

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

});

});

</script>

</head>

<body>

<select id=”cityId”>

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

<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>

<script type=”text/css”>

.Hilight:

bigground-color:pink;

}

</style>

<script type=”text/javascript” src=”jQuery.js”>

</script>

<script type=”text/javacript”>

$(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>

<div id=”myDiv” style=”width:400px;height:200px;border:2px solid black;”>

This is my div This is my div This is my div This is my div

</div>

</body>

</html>

<html>

<head>

<script type=”text/css”>

.Hilight: bigground-color:pink;

}

</style>

<script type=”text/javascript” src=”jQuery.js”>

</script>

<script type=”text/javacript”>

$(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>

<div id=”myDiv” style=”width:400px;height:200px;border:2px solid black;”>

This is my div This is my div This is my div This is my div 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>

<script type=”text/css”>

.Hilight: bigground-color:pink;

}

</style>

<script type=”text/javascript” src=”jQuery.js”></script>

<script type=”text/javacript”>

$(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>

<div id=”myDiv” style=”width:400px;height:200px;border:2px solid black;”>

This is my div This is my div This is my div This is my div 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”/>

<p class=”someclass”/>

<div class=”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

<span class=”someclass”/>

<p class=”someClass”/>

<div class=”someclass”/>

<html>

<head>

<script type=”text/javascript”src=”jQuery.js”></script>

<script type=”text/javascript”>

$(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>

<table boarder=”1”>

<tr>

<td>Name</td>

<td> <input type=”text”,name=”name”/> </td>

</tr>

<tr>

<td> Password </td>

<td> <input type=”password” name=”password” /> </td>

</tr>

<tr>

<td> Address</td>

<td> <textarea cols=”50” rows=”4”></textarea> </td>

</tr>

<tr>

<td>Phone</td>

<td> <input type=”submit” id=”AddPhoneButton” value=”AddPhone”/>

<div id=”PhoneDiv”> <div id=”PhoneTypeDiv” style=”float:left”>

<select name=”PhoneType”>

<option value=””>Select One</option>

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

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

<option value=”Home”>Home</option>

</select>

</div>

<div id=”PhoneNumberDiv” style=”float:left”>

<input type=”text” name=”PhoneNumber”/>

</div>

</div>

</td>

</tr>

<tr>

<td>City</td>

<td> <select id=”cityID”>

<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 colspan=”2” align=”center”> <input type=”submit” value=”submit”/> </td>

</tr>

</table>

<button>Release Event Handlers</button>

</body>

</html>
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