prototype javascript library try.these example

<script type="text/javascript" charset="utf-8">
 function doc (argument) {
  document.write(argument);
  document.write("<br />\n");
 }
 var rs = Try.these(
       function() {return new XMLHttpRequest()},
       function() {return new ActiveXObject('Msxml2.XMLHTTP')},
       function() {return new ActiveXObject('Microsoft.XMLHTTP')}
     );
 doc(rs);
 
 var lambda = function() {return new ActiveXObject('Msxml2.XMLHTTP')};
 try {
  lambda();
 } catch (e) {
  doc(e);
 }
</script>