Compare emails to check if they are equal gives error

I would like help with this question. If email1 and email2 (Strings) are equal when submit is pressed, an alert message box will be displayed. I didn’t add an else statement.

Error:

Uncaught ReferenceError ReferenceError: email1 is not defined
at (script.js:7:17)

function equals_function(email1, email2) {
  if (email1 != email2) {
    alert("You didn't enter matching email addresses in the input!") // output alter
  }
}

equals_function(email1, email2)
<form>
  <label for="email1">Email Address:</label>
  <input type="text" name="emailone" id="emailone">

  <p>
    <label for="email2">Email Address Confirmation:</label>
    <input type="text" name="emailtwo" id="emailtwo">
  </p>
  <p><input type="submit"></p>
</form>