How to set a form field using javascript

I have a jsp and there are some fields in the form. The fields are dynamical, such as question_1, question_2, question_3, ..., question_i, in which 'i' is dynamical. Beside each fields I suppose to put a 'default' button. When user click the button, the field can be set a default value.
I think i can use a javascript function to realize it.
The function could be like this:
function doDefault_questionBreak(defaultvalue,i){
document.forms[0].question_i.value = defaultvalue;
}
How can i use the parameter 'i' to set a value(defaultvalue) to its field (question_i)? Maybe it's a javascript question.
Thank in advance.

Using Java Script, u will be able to change the value inside a field on the form(gui), but you can not change the actual serverside value. You can use the server side value though.
I don't know if that answered your question.
Kishore.

Please be sure to place question in the appropriate forum. Since this is a Javascript question, this is better asked in the HTML/Javascript forum.
Moving to that forum.
thanks,
bear
JSP Forum Bartender

Basic Idea:
document.formName["standardName_" + variable].value = "BLAH";

Hi Kishore,
Thank your response.
When user click the 'default' button, the field is set to a value, it is the same as user inputs a value. After that the form is submit and the server can get the value.
But my question is how to write the field name question_i?
'i' is a parameter, absolutely i can't write as 'question_i', so what is the correct way?
Thanks,
Chris

Eric,
Thank you very much.
That's what i want. I solved the problem!
Regards,
Chris