How to shift and unshift using JavaScript?

<script type="text/javascript">

var numbers = ["one", "two", "three", "four"];

numbers.unshift("zero");

document.write(" "+numbers.shift());

document.write(" "+numbers.shift());

document.write(" "+numbers.shift());

</script>

This produces

zero one two

shift, unshift, push, and pop may be used on the same array. Queues are easily implemented using combinations.