Ignore Defense Calculator (MapleStory)

HTML

<textarea id="numberEntry" autofocus="autofocus" placeholder="Incorrect: ,test , 78% ,tester ,75%,,  |  Correct: 78%, 75%" value="10%, 5%, 5%, 10%, 6%, 18%, 30%, 8.5%, 20%"></textarea>
<input type="submit" value="Submit" onclick="calculate()">
<input id="output" type="text" disabled="disabled" value="0%">

CSS

html,
body,
textarea {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100%;
}

textarea {
  height: 95%;
  border: 1px solid red;
}

JavaScript

function calculate() {
  var values = document.getElementById("numberEntry").value,
    valueList = values.split(/[\s,]+/),
    numbers = [],
    current = 1;
  for (var i = 0, vI = valueList.length, mark = "", value; i < vI; i++, mark = "") {
    value = valueList[i].replace("%", '').replace("*", '');
    if (isNumeric(value)) {
      if (value < 101 && value > 0)
        current *= (1.0 - parseFloat(value / 100.0)).toFixed(2);
      else
        mark = "*";
      numbers.push(mark + parseFloat(value) + "%");
    }
  }
  document.getElementById("numberEntry").value = numbers.join(", ");
  document.getElementById("output").value = ((1 - current) * 100.0).toFixed(2) + "%";
}

function isNumeric(n) {
  return !isNaN(parseFloat(n)) && isFinite(n);
}