how to set selected value of dropdown in jquery using id code example

Example 1: set select option as selected jquery

$(document).ready(function() {
    $("#gate option[value='Gateway 2']").prop('selected', true);
    // you need to specify id of combo to set right combo, if more than one combo
});

Example 2: jquery set select value

$("div.id_100 select").val("val2");