Ayuda con select y javascript

[America|UNK]

Código Javascript:

<script>
function fn(el){
    var v=el.options[el.selectedIndex].value,s=el.form.result2,
    o=s.options,l=o.length,i,j=s.value==v
    for(i=0;i<l;i++)o[i].disabled=o[i].value==v?!!1:!1
    if(j)s.selectedIndex=-1
}
</script>
 

Código HTML:

<form>
    <select name="result1" onchange="fn(this)" multiple="1">
        <option value="val1">Valor 1</option>
        <option value="val2">Valor 2</option>
        <option value="val3">Valor 3</option>
    </select>
 
    <select name="result2" multiple="1">
        <option value="val1">Valor 1</option>
        <option value="val2">Valor 2</option>
        <option value="val3">Valor 3</option>
    </select>
<form>