Math.round Rounds Up
luljs still worksRound a score of 2.5 and get 3, but round -2.5 and get -2.
In 2026: Still works. Math.round always rounds a half toward positive infinity, not away from zero. So 2.5 goes up to 3 and 0.5 goes up to 1, but -2.5 goes up to -2 and -0.5 goes up to -0. Rounding a column of negative halves quietly biases them one way.
Where it came from: Math.round rounds halves toward positive infinity, documented on MDN, which is why negative halves round the opposite way to positive ones.
MDN ↗
<script>
document.write('<p><code>Math.round(2.5)</code> is <b>' + Math.round(2.5) + '</b>, <code>Math.round(-2.5)</code> is <b>' + Math.round(-2.5) + '</b></p>');
var nh = Math.round(-0.5);
document.write('<p><code>Math.round(0.5)</code> is <b>' + Math.round(0.5) + '</b>, <code>Math.round(-0.5)</code> is <b>' + (Object.is(nh, -0) ? "-0" : nh) + '</b></p>');
document.write('<p>Halves always round toward +Infinity, not away from zero. String() hides the minus on -0, so it is printed here through Object.is.</p>');
</script>