assign value of a text field in html from a javascript variable

I defined a javascript object say var obj and I want to assign its value to the value of a text field <input type="hidden" name="hiddenValue"value= > in order to be submitted within a form object. But I am not familiar with the syntax on how to do that.

[271 byte] By [fab3a] at [2007-11-27 10:26:50]