Array.sort() はさまざまなブラウザ間で安定していますか?

<code class="js">function Pair(_x, _y) {
  this.x = _x;
  this.y = _y;
}
function pairSort(a, b) {
  return a.x - b.x;
}
// Create an array with enough entries to trigger the "more efficient" sort method
var y = 0;
var check = [];
while (check.length < 100) {
  check.push(new Pair(Math.floor(Math.random() * 3) + 1, ++y));
}
check.sort(pairSort);
// Check for instability by comparing the order of equal elements
var min = {};
var issues = 0;
for (var i = 0; i < check.length; ++i) {
  var entry = check[i];
  var found = min[entry.x];
  if (found) {
    if (found.y > entry.y) {
      console.log("Unstable at " + found.i + ": " + found.y + " > " + entry.y);
      ++issues;
    }
  } else {
    min[entry.x] = {x: entry.x, y: entry.y, i: i};
  }
}
// Log stability status
if (!issues) {
  console.log("Sort appears to be stable");
}</code>