Based on your comment that it does not generate your list, and Jared comments that you are trying to add parameters, try something like this:
var list = document.getElementById('theSelector'); var newOp = document.createElement("option"); newOp.text = "Txt"; newOp.value = "1"; list.options.add(newOp);
EDIT
According to Jared, the following may offer you a performance advantage:
list.options[list.options.length] = newOp;
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