Microsoft® JScript® ubound Method 
Language Reference Version 3

Returns the highest index value used in the specified dimension of the VBArray.
safeArray.ubound(dimension)The ubound method syntax has these parts:
Part Description safeArray Required. A VBArray object. dimension Optional. The dimension of the VBArray for which the higher bound index is wanted. If omitted, ubound behaves as if a 1 was passed.
If the VBArray is empty, the ubound method returns undefined. If dim is greater than the number of dimensions in the VBArray, or is negative, the method generates a "Subscript out of range" error.The following example consists of three parts. The first part is VBScript code to create a Visual Basic safe array. The second part is JScript code that determines the the number of dimensions in the safe array and the upper bound of each dimension. Both of these parts go into the <HEAD> section of an HTML page. The third part is the JScript code that goes in the <BODY> section to run the other two parts.
<HEAD> <SCRIPT LANGUAGE="VBScript"> <! Function CreateVBArray() Dim i, j, k Dim a(2, 2) k = 1 For i = 0 To 2 For j = 0 To 2 a(j, i) = k k = k + 1 Next Next CreateVBArray = a End Function > </SCRIPT><SCRIPT LANGUAGE="JScript"> <! function VBArrayTest(vba) { var i, s; var a = new VBArray(vba); for (i = 1; i <= a.dimensions(); i++) { s = "The upper bound of dimension "; s += i + " is "; s += a.ubound(i)+ ".<BR>"; return(s); } } > </SCRIPT> </HEAD>
<BODY> <SCRIPT language="jscript"> document.write(VBArrayTest(CreateVBArray())); </SCRIPT> </BODY>