var normalizeWheelDelta = function() {

  // Keep a distribution of observed values, and scale by the

  // 33rd percentile.

  var distribution = [], done = null, scale = 30;

  return function(n) {

    // Zeroes don't count.

    if (n == 0) return n;

    // After 500 samples, we stop sampling and keep current factor.

    if (done != null) return n * done;

    var abs = Math.abs(n);

    // Insert value (sorted in ascending order).

    outer: do { // Just used for break goto

      for (var i = 0; i < distribution.length; ++i) {

        if (abs <= distribution[i]) {

          distribution.splice(i, 0, abs);

          break outer;

        }

      }

      distribution.push(abs);

    } while (false);

    // Factor is scale divided by 33rd percentile.

    var factor = scale / distribution[Math.floor(distribution.length / 3)];

    if (distribution.length == 500) done = factor;

    return n * factor;

  };

}();

​

// Usual boilerplate scroll-wheel incompatibility plaster.

​

var div = document.getElementById("thing");

div.addEventListener("DOMMouseScroll", grabScroll, false);

div.addEventListener("mousewheel", grabScroll, false);

​

function grabScroll(e) {

  var dx = -(e.wheelDeltaX || 0), dy = -(e.wheelDeltaY || e.wheelDelta || 0);

  if (e.detail != null) {

    if (e.axis == e.HORIZONTAL_AXIS) dx = e.detail;

    else if (e.axis == e.VERTICAL_AXIS) dy = e.detail;

  }

  if (dx) {

    var ndx = Math.round(normalizeWheelDelta(dx));

    if (!ndx) ndx = dx > 0 ? 1 : -1;

    div.scrollLeft += ndx;

  }

  if (dy) {

    var ndy = Math.round(normalizeWheelDelta(dy));

    if (!ndy) ndy = dy > 0 ? 1 : -1;

    div.scrollTop += ndy;

  }

  if (dx || dy) { e.preventDefault(); e.stopPropagation(); }

}

​