Penggunaan Shift dan unShift pada Queue

?html>
?head>
?title>Program Queue degan Shift dan Unshift JavaScript?/title>
?script language = "JavaScript">

function DataQueue()
{
var queue = [];
queue.unshift(1);
queue.unshift(2);
var i = queue.shift();
document.write(i + "?br />");

queue.unshift(3);
queue.unshift(4);
var i = queue.shift();
document.write(i + "?br />");
}

?/script>
?/head>

?body>
?form name="FormStrukturData">
?input name="btnQueue" value="Queue" type="button" onClick="DataQueue();" />
?/form>
?/body>
?/html>