I think there are several ways to do this. The easiest way:
$("#dropdownID").val("dropdownValue");
This will work fine, but it will not fire the change event, if any. To solve the problem, use it as shown below:
$("#dropdownID").val("dropdownValue").change();
Other possible ways:
$("#dropdownID").attr('selected','selected'); $("#dropdownID").prop('selected', true);
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