SO jQuery Fiddle
Test Fiddle mainly for SO Questions jQuery 1.4.3, UI 1.8.5
HTML
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.5/themes/ui-lightness/jquery-ui.css">
JavaScript
var myArray = [1,2,3,4];
var myString = myArray.join(', ');
alert(myString);