Difference between function(e) and function()

Question

What is the significant/difference between the following code? (e) at the end

jQuery(document).on( 'click', '.something', function(e) {
vs.
jQuery(document).on( 'click', '.something', function() {

Thanks!

• Josh Crozier: The first one passes the event object to the anonymous function, whereas the second one doesn't. Try logging the variable. See: api.jquery.com/category/events/event-object
• user2864740: Technical details: The event object is always passed to the 'on' callback function as the first argument (per the documentation), but only the function with a parameter can access the supplied argument by the e name - if accessing such is not required then the parameter can be safely omitted and it will not affect the program. In both cases the supplied argument(s) can be accessed via arguments.

Answer 1

There is technically no difference in the 2 expressions. 'e' refers to the event variable which is optional and works more like this expression in jquery. you can use that e variable to figure out certain information like the target which invoked the event or any other property.

jQuery(document).on( 'click', '.something', function() {
 alert(this.id); // gives you the id of the element using this
}); 
jQuery(document).on( 'click', '.something', function(e) {
 alert(e.target.id); // gives you the id of the element using event
});

In my opinion, the biggest advantage of using the event e is that it gives you more correct info compared to this when the event handlers are invoked over the document.

$(document).on('click',function()
{
 alert($(this).attr("id")); // id as undefined
})
$(document).on('click',function(e)
{
 alert(e.target.id); // gets the correct id
})

Example : http://jsfiddle.net/twjwuq92/

Answer 2

The e parameter is the event triggered, which is the jQuery event object. Both the cases, event is created, but to access it, we are passing it as parameter.

// Case 1
jQuery(document).on( 'click', '.something', function(e) {
 e.which; // Short form. This is Click Event object.
});
// Case 2
jQuery(document).on( 'click', '.something', function() {
 // There's no reference to the event that's triggered.
});

• nderscore: window.event is a microsoft-specific implementation and not standard.
• nderscore: The window.event object only exists for IE. It's not correct still.
• JJJ: event is not the same object as the one jQuery passes to the callback.
• Praveen Kumar Purushothaman: @Juhana I have given the reference to the jQuery event object only. Check please.
• Josh Crozier: @PraveenKumar Your second example would throw ReferenceError: event is not defined in FF.