Exploring queryCommandEnabled() vs onbefore* events

queryCommandEnabled.js

<pre></pre>
<script>
var pre = document.getElementsByTagName('pre')[0];

document.onbeforepaste = document.onbeforecopy = document.onbeforecut = function (e) {
    pre.appendChild(document.createTextNode(e.type));
}

for(var cmd in {'copy':1, 'cut':1, 'paste':1}){
    pre.appendChild(document.createTextNode('\n\n' + cmd.toUpperCase() + '\n'));
    pre.appendChild(document.createTextNode('queryCommandSupported(): ' + document.queryCommandSupported(cmd) + '\n'));
    try{
        pre.appendChild(document.createTextNode('queryCommandEnabled(): ' + document.queryCommandEnabled(cmd) + '\n'));
    }catch(e){
        pre.appendChild(document.createTextNode('queryCommandEnabled throws: '+e))
    }

}
</script>