HTMLMultibox manipulation in JavaScript (Struts)

[fam2315]

I have a multibox in one of my JSP's that I want to manipulate via JavaScript, and have one of the
checkboxes selected.

The multibox property is "allChoices"

in JavaScript, how do I reference the first checkbox in the multibox?

The code I have now does not seem to be working:

var choice1 = document.getElementById("allChoices[0]");

choice1.checked = true;

[Tolls]

You'd do better at a Javascript forum, since this is a Javascript question really.