Edit in JSFiddle

var a = 1;
var d;
function test() {
  b = 5;
  var c = 7;
}

function log(txt){
	$('#console').html($('#console').html() + "<br/>"+ txt);
}

$(document).ready(function() {
	test();
  if(typeof a != 'undefined')log("a result::" + a);
  if(typeof b != 'undefined')log("b result::" + b);
  if(typeof c != 'undefined')log("c result::" + c);
  if(typeof d != 'undefined')log("d result::" + d);
  
  if(typeof d == 'undefined'){
  	log("d is undefined");
  }
  
});

<div id="console">
</div>