Need help with Click()

I'm new to JS and i'm trying to write a script that will do something like this:

If on page #1
//click button1
else if on page#2
//click button2
else
//click button3

To click a button i use:
document.Form_Name.Button_Name.click();

It works fine as long as i know the form name and the button name like clicking the search button in google would be:
document.f.btnG.click();

But some forms don't have a name. All they have is something like:
<form action="Link" method="post" onsubmit="this.submit.disabled=true;">
.
.
.
and the button is:
<input name="submit" type="submit" onload="this.disabled=false;" value="OK">


How can i click such a button?

 

You can loop through all forms on a document this way :

Code:

var AllForms = document.forms;
var TForm;
for (i = 0; i < AllForms.length; ++i)
{
      TForm = document.forms[i];
      // To click a button
      TForm.mybutton.click();
}

It depends on you to check which form you want : you can check properties of TForm before clicking button.