how to change selected option in jquery 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: change value of drop down using jquery

$('#ddlID').val('New_OptionValue').change()

Example 3: jQuery change select value

$("#mySelectElementID").val("my_new_value"); //change selected option/value with jQuery