fact.js

  function calculate_fact() {
    clearFields();
    expand_eval();
    var num;
    num = document.getElementById("num").value;
    if (num >= 0) {
      addToEval(fact(num));
      Materialize.toast("You've been factorialed!", 4000) // 4000 is the duration of the toast
    }
    else {
      Materialize.toast("Invalid! Insert positive integer!", 4000) // 4000 is the duration of the toast
    }
  }

  function addToEval(str) {
    $("#evaluation").append(str, "<br />");
  }

  function expand_eval() {
    var elem = $("#evaluation");
    var currHeight = elem.height();
    var autoHeight = elem.css('height', 'auto').height();
    elem.height(currHeight).animate({
      height: autoHeight
    }, 1000)
  }

  function fact(n) {
    if (n == 0) return 1;
    var val = n * fact(n-1);
    addToEval(n + "! = " + val);
    return val;
  }

  function clearFields() {
      document.getElementById("evaluation").innerHTML = "";
  }