javascript - display items in listbox matching the keys pressed

Question

i have a web page with a textbox and a listbox.
the data to be displayed in the listbox is stored in an array on the client side.
i need to trap the keys when the users types in the textbox, and display the data related
to it from the data stored inn the array and populate the listbox(on the client side).

thanks
any kind of help would be appreciated