JavaScript Fibonacci Sequence

function fibonachi() {
    var n = parseInt(document.getElementById('inputFib').value);
    var f = 0;
    var s = 1;
    var t;
    var sum = 0 + 1;

    for (var i = 1; i < n - 1; i++) {

        t = f + s;
        f = s;
        s = t;

        sum += t;
     }

     document.getElementById('resultFib').innerHTML = "The sum of the first " + n + " numbers of the Fibonacci sequence is: <p style='color: red; margin: 5px 0; font-size: 30px;'>" + sum + "</p>";
}