Visual Basic programmers are familiar with control arrays but they may be unfamiliar to users of other languages. Control arrays are generally characterized by having a number of controls which have the same name and are then referred to via an index. Like other Javascript indices, control array indices range from 0 to n; i.e., they are zero-based but the zero index holds the array length. Unfortunately, unlike VB control arrays, Javascript control arrays do not return an index when they are clicked unless you specifically program it into the value or an onclick handler.

Although the Javascript control array which is best documented is that for radiobuttons, other controls can be arrayed as well.

This little form has nine checkboxes. Each has the name 'checkArray'. Each has also been assigned a value equivalent to the spelled out number of its index. The zero index holds array length. When you click the button, a function will attempt to tell you which ones are checked by iterating through the control array.
 

(1)The array is recognized and the function can tell me the number of controls in it.
(2)The array name is undefined.
(3)The value of any member of the array is defined.
(4)In Netscape 2.0x, the order of the array elements MAY appear backwards. If this happens, include a dummy 'onclick' handler for each button and the array will line up correctly.