View Full Version : Find input name with input's id

06-01-2009, 11:58 PM
I'm building a page which has an input box that frequently changes its name attribute using innerHTML. However, the id ("sf") always stays the same. How would I find the current name of the input using JavaScript? And is it possible to find the value of the input box using getElementById? If not, how would I find the value of the input box, if the name changes?

For instance...say the name was "q". I would access it normally using document.f.q.value. However, since the name changes, that won't always work. If I were to find the name, and then set it to a variable, how would I then find the value of the input? Say the variable would be "qvar"...wouldn't document.f.qvar.value look for an input with the name "qvar"? Would 'document.f.'+qvar+'.value' work?

<form name="f">
<input type="text" name="q" id="sf">

Old Pedant
06-02-2009, 12:42 AM
is it possible to find the value of the input box using getElementById?

var theValue = document.getElementById("sf").value;

The longer way--clearly not needed here, but for future reference:

var fld = document.getElementById("sf");
var fldname = fld.name;
var theValue = document.f.elements[fldname].value;

06-02-2009, 01:13 AM
Everybody's favorite faq:

http://www.jibbering.com/faq/faq_notes/square_brackets.html :cool:

06-02-2009, 03:58 AM
var theValue = document.getElementById("sf").value;


Wow. That was incredibly simple...I thought I had tried that before, I guess I must have done something wrong. It works great. Thanks!

Everybody's favorite faq:

http://www.jibbering.com/faq/faq_notes/square_brackets.html :cool:

I had no idea bracket notation applied to so many things. I've used them before in frames, and some other things...I will definitely remember it in the future!