Set select option 'selected', by value

Question

I have a select field with some options in it. Now I need to select one of those options with jQuery. But how can I do that when I only know the

Answer 1

$('#graphtype option[value=""]').prop("selected", true);

This works well where #graphtype is the id of the select tag.

example select tag:

 
    Site 
    SiteA
    SiteB