Fibonacci Sequence in JavaScript

just as the title says

by Joseph Tate

HTML

<h1>Fibonacci sequence</h1>

<input type=text id=number value=3 onchange="$('#output').text(fib($('#number').val()))" />

<p>Output: <span id=output></span></p>

<script>
    function fib (n) {
        n = parseInt(n, 10);
        if (n < 1) {
         // error
         return 0;
        }
        if (n===1 || n===2) {
         return 1;
        }
        return fib(n-2) + fib(n-1);
    }
</script>