Question

In JQuery is it possible to skip an optional argument and pass the next ones? if yes, how a jquery function determines which value is for which parameter?

An example:

//
// function signature is
// jQuery.get( url [, data] [, success(data, textStatus, jqXHR)] [, dataType] )
//
// function is called as
//
$.get('ajax/test.html', function (data) {
    $('.result').html(data);
    alert('Load was performed.');
});

In call to $.get() after the url the [, data] is skipped and next the success callback is passed.

Answer 1

Yes it is possible to skip optional arguments, even from the middle. jQuery looks at the type of arguments to determine which is which. Have a look at the signature of jQuery.load:

.load(url [, data] [, complete(responseText, textStatus, XMLHttpRequest)])

And the following work as expected:

.load("test.php")
.load("test.php", {foo: bar})
.load("test.php", {foo: bar}, function(){})
.load("test.php", function(){}) // you skipped the 2nd parameter? no.

You’ll notice that the three parameters are: string, object and function. Inside the function jQuery can easily check how many arguments were passed and their types. If it notices that the 2nd parameter is a function it will assume that data parameter was skipped and act accordingly.

To your surprise, there is another jQuery.load function with different signature which does something entirely different:

.load(handler(eventObject))
.load([eventData], handler(eventObject))

Again, jQuery can determine which method to fire by looking at the arguments.