javascript - Context menu not showing -

i have strange javascript issue.

this code supposed show context menu, doesn't:

$find('rcmunit').showat(document.getelementbyid('x').value, document.getelementbyid('y').value); 

but if add alert box it, menu shows, alert box:

$find('rcmunit').showat(document.getelementbyid('x').value, document.getelementbyid('y').value);alert('x'); 

i'm not totally sure, i'll believe should use settimeout , work:

function showmenu() {  $find('rcmunit').showat(document.getelementbyid('x').value,        document.getelementbyid('y').value); }  settimeout('showmenu()',500);