Question

How would you write a script to disable a select if you have two selects (both with ids) and an option in the first select is selected.

Answer 1

Since you have tagged the question with jQuery, I’ll give you an idea of how to do it using jQuery:

$("#firstSelectId").change(function() {
    var first = $(this);
    $("#secondSelectId").prop("disabled", function() {
        return first.val() === "whatever";
    });
});

Note that the above assumes you want to enable the second select again if a different option was selected. Here’s a working example.