[jQuery] div display help

[jQuery] div display help


I am having some trouble getting some divs to display dynamically. Can
someone please offer a pointer?
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<script type="text/javascript">
function update(x){
    var id = x.selectedIndex;
    var v = x.options[id].value;
    var f = "test" + v;
    var c = document.getElementByID(f);
    c.style.display = "block";
}
</script>
<html>
    <div id="test" style="display:block">
    testing div
    </div>
    <div id="x">
        <select name="t" id="t" onchange="update(this);">
        <option value=1>one</option>
        <option value=2>two</option>
        </select>
    </div>
    <div id="test1" style="display:none">
        this is some stuff
    </div>
    <div id="test2" style="display:none">
        this is some other stuff
    </div>
</html>
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