Here are some of the techniques using which you can select the drop down values.
Method 1:
$('#drpSelectSourceLibrary option')[2].selected = true;
Method 2:
$('#x option[value="5"]').prop('selected', true);
Method 3:
$("#drpSelectSourceLibrary").val('ValueFour');
method 4:
$('select').val("ValueOne");
One can refer this blog
Selecting dropdown values in javascript. There are so many techniques to do it.