The result is twice the input value.
Input >>

Result >>
A copy of the JavaScript functions in the head element:

// sample-6-form-functions.js
// This sample corresponds to "Accessing forms with JavaScript 1) in my lecture notes
// This sample uses getElementById() to find the form
// Then it finds the result element as a child of the form

// reset validation function
// returns false if the reset element value is an empty string
// otherwise returns true
function validate()
  {
  var rc = false;
  var form_element = document.getElementById("only-form");
  var result_element = form_element.result;
  // The value of the result is always set to "" either
  // by the body onload call to the loaded() function, or
  // by the input onchange call to the changeInput() function
  // unless the changeInput has set it to a numeric value.

  // check the value attriabute of the result element
  if(result_element.value != "")
    {
    rc = true;
    }
  return rc;
  }

// ----------------------------------------------------------------------------
// the functions loaded() and changeInput() are the same as in previous samples.
// see the previous examples for the code for these two functions.