Set the selected index of a Dropdown using jQuery

I'm writing this answer in 2015, and for some reason (probably older versions of jQuery) none of the other answers have worked for me. I mean, they change the selected index, but it doesn't actually reflect on the actual dropdown.

Here is another way to change the index, and actually have it reflect in the dropdown:

$('#mydropdown').val('first').change();

Just found this, it works for me and I personally find it easier to read.

This will set the actual index just like gnarf's answer number 3 option.

// sets selected index of a select box the actual index of 0 
$("select#elem").attr('selectedIndex', 0);

This didn't used to work but does now... see bug: http://dev.jquery.com/ticket/1474

Addendum

As recommended in the comments use :

$("select#elem").prop('selectedIndex', 0);

First of all - that selector is pretty slow. It will scan every DOM element looking for the ids. It will be less of a performance hit if you can assign a class to the element.

$(".myselect")

To answer your question though, there are a few ways to change the select elements value in jQuery

// sets selected index of a select box to the option with the value "0"
$("select#elem").val('0'); 

// sets selected index of a select box to the option with the value ""
$("select#elem").val(''); 

// sets selected index to first item using the DOM
$("select#elem")[0].selectedIndex = 0;

// sets selected index to first item using jQuery (can work on multiple elements)
$("select#elem").prop('selectedIndex', 0);