Event.stopPropagation() and Event.preventDefault()

1. event.stopPropagation() stops an event from bubbling up the event chain

2. event.preventDefault() will only prevent browser’s default action on that event from occurring, but the event still propogates up the event chain.


Example

$("#myDiv").click(function() {
   alert('click on #myDiv');
});

$("#divButton").click(function(e) {
   alert('button click');
   e.stopPropagation();
});

Detecting an undefined object in JavaScript

typeof allows the identifier to never been declared before

if (typeof obj == "undefined")

instead of

if(obj == null) // will throw an error due to never declared

How to stop caching with jQuery ($.get(), $.ajax() etc) and javascript

To make it unique for each passes, we can place in a random number behind the url as shown below

$.get('remoteUrl.do?'+Math.random()+, function(data){

	$('#msg'+id).html(data);

}, 'html');

Set cache:false 

$.ajax({

	url: 'remoteUrl.do',

	cache: false,

	success: function(data){

		$('#resultDiv').append(data);

	} }); 

$.ajaxSetup({

	cache: false

});

Disable caching using html meta tag:

<meta equiv="cache-control" content="no-cache"><meta equiv="expires" content="0"><meta equiv="pragma" content="no-cache">

JQuery

jQuery is a Open source JavaScript Library.

jQuery is easy to learn.

Fast, Easy to use, Easy-to-use AJAX (I love the $.ajaxSetup() function)
Nice Event handlers
CSS selectors


features:

* HTML element selections
* HTML element manipulation
* CSS manipulation
* HTML event functions
* JavaScript Effects and animations
* HTML DOM traversal and modification
* AJAX
* Utilities