Use JavaScript to change the href Tag depending on input field

There are a few issues with your JavaScript.

<script language="JavaScript">

function login()
var password = getElementById("password"); // this gets the element, not the value of the element
{ // this curly brace is in the wrong place
if (password = "wima") { // this sets the value of the password var to "wima" 
getElementById("submit").href="/pages/home.html";
}
else {
getElementById("submit").href="index.html";
}
} 
</script>

Here is your code, cleaned up.

<script language="JavaScript">

function login() {
    var password = document.getElementById("password").value;
    if (password == "wima") { // use == to compare value
        document.getElementById("submit").href="/pages/home.html"; 
    }
    else {
        document.getElementById("submit").href="index.html";
    }
}
</script>

Another issue here is that you shouldn't be changing the href on the element used to execute the login() function.

You could redirect the user to the new page like so:

   <script language="JavaScript">

    function login() {
        var password = document.getElementById("password").value;
        if (password == "wima") { 
            window.location.href="/pages/home.html";
        }
        else {
            window.location.href="index.html";
        }
    }
    </script>

Here is a form validator with a switch.

function validateForm() {
  var x = document.forms["myForm"]["password"].value;

  switch (x) {
    case "":
      alert("Name must be filled out");
      return false;
      break;

    case "wima":
      return true;
      break;

    default:
      alert("Error: Wrong Password.");
      document.location.href = "https://stackoverflow.com/search?q=notloggedin";
      // Replace the link above with your error link return
      return false;
  }

}

<!-- Replace action link with your successful link -->
<form name="myForm" action="https://stackoverflow.com/search?q=login" onsubmit="return validateForm()" method="post">
  <input type="password" name="password">
  <input type="submit" value="Submit">
</form>

Your password is visible in text if someone inspects the html/javascript. So this method of security is not advised. For basic concepts it is interesting to have a link change based on input. Try this.

<p>

  Username
  <input id="username" type="text" placeholder="WIMA"><br> Password
  <input id="password" type="password" placeholder="WIMA"><br>

  <a class="button" id="submit" >
    Submit 
    </a>
</p>
<script>
    var password = document.getElementById('password');
    password.addEventListener('change', enableLogin);
    var submit = document.getElementById('submit');

    function enableLogin() {
      if (password.value == "wima") { // it is an easy mistake (= or ==)
        submit.href = "/pages/home.html";
      } else {
        submit.removeAttribute('href');
      }
    }
</script>

A few things happened here:

• The value inside a <input> is accessed by .value;
• You misplaced the {
• getElementById is not a global method it has to be called on the element you want to select in (in your case the document itself)
• To test if two values are equal use === in js

function login() {
  var password = document.getElementById("password").value;
  if (password === "wima") {
    document.getElementById("submit").href = "/pages/home.html";
  } else {
    document.getElementById("submit").href = "index.html";
  }
}

<p>

  Username
  <input id="username" type="text" placeholder="WIMA"><br> Password
  <input id="password" type="password" placeholder="WIMA"><br>

  <a class="button" id="submit" href="#" onclick="login()">
    Submit 
    </a>
</p>