Untitled

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
</head>
<body>

<script id="jsbin-javascript">
"use strict";

ar = [5, 10, 3, 6, 999999, 10000000];

function aVeryBigSum(ar) {
  var theSum = ar.reduce(function (accumulator, currentValue) {
    return accumulator + currentValue;
  });
  return theSum;
}

console.log(aVeryBigSum(ar));
</script>


<script id="jsbin-source-javascript" type="text/javascript">ar = [5, 10, 3, 6, 999999, 10000000];

function aVeryBigSum(ar) {
  let theSum = ar.reduce((accumulator, currentValue) => accumulator + currentValue);
  return theSum;
}


console.log(aVeryBigSum(ar));</script></body>
</html>