not as yours. see below:
var a=new Array();
a[0]=new Array();a[0][0]="a";a[0][1]="aa";......
a[1]=new Array();a[1][0]="b";a[1][1]="bb";......
var a=new Array();
a[0]=new Array();a[0][0]="a";a[0][1]="aa";......
a[1]=new Array();a[1][0]="b";a[1][1]="bb";......
<script>
var a = new Array();
a[0] = ['11','12'];
a[1] = ['21','22'];
alert(a[0][0]);
</script>