Greeting the forum;

I am having trouble wit ha Javascript function that interacts with a form's select box and textarea. The selectbox has a number of options to choose from, with the default selection telling the visitor to choose from the flyout list. The textarea has a default readonly message upon page loading. The script I have, which is typed below, will only change the textarea to the first option, called "Proposal A" no matter what other choices I make in the select box. I want it to change to any and all options and input then into the textarea for the user to make his/her final choice before submitting the form (it is a voting type of form).

Here is my current code for the select box on the form page:
                 <select name="Proposals" onchange="loadComments()">
                  <option selected>Choose a Proposal here</option>

                  <option>Proposal A </option>

                  <option>Proposal B </option>

                  <option>Proposal C </option>

                  <option>Proposal D </option>
Here is the Javascript code from an external js file:
function loadComments()
  //var f1 = document.form.Proposals.selectedIndex
  var f1 = document.form.Proposals[document.form.Proposals.selectedIndex].value
  var f2 = document.form.Comments
  var txt1 = "Testing the script for Proposal A"
  var txt2 = "Testing the script for Proposal B"
  var txt3 = "Testing the script for Proposal C"
  var txt4 = "Testing the script for Proposal D"

  if (f1 = 1) 
    f2.value = txt1

  else if (f1 = 2)
    f2.value = txt2

  else if (f1 = 3)
    f2.value = txt3

  else if (f1 = 4)
    f2.value = txt4
Any help will be appreciated. Thanks in advance.