Cannot end Prompt Box process in a do while loop

Question

I have small question about ending this java script process when the user enters the number 999 in the prompt box, because instead of doing that, it just takes the 999 and treats as any other number entered. How can I prevent this from happening? Thanks.

<script>
    var entry;
    do {
        entry = prompt("Enter degrees in Fahrenheit\n" +
                       "Or enter 999 to end entries", 999);
        entry = parseInt(entry);

        window.alert("Fahrenheit = " + entry +
        "\nCelcius = " + ((entry - 32) * (5/9)) + " degrees");

    } while (entry != 999);
</script>

Answer 1

Try this:

var entry;
while (true) {
      entry = prompt("Enter degrees in Fahrenheit\n" + "Or enter 999 to end entries", 999);
  
  if (entry==999) {
    break;
  }
    entry = parseInt(entry);

    window.alert("Fahrenheit = " + entry + "\nCelcius = " + ((entry - 32) * (5/9)) + " degrees");

}