jquery set dropdown by value code example
Example 1: set dropdown in jquery
$('select[name^="salesrep"] option[value="Bruce Jones"]').attr("selected","selected");
Example 2: how to set dropdown value in jquery
$("#comboboxid").val(yourvalue).trigger("chosen:updated");
Example 3: set dropdown in jquery
$('select[name^="salesrep"] option:selected').attr("selected",null);