events: Faster ascending array index

lib/events.js

@@ -426,9 +426,21 @@ function spliceOne(list, index) {
   list.pop();
 }
 
-function arrayClone(arr, i) {
-  var copy = new Array(i);
-  while (i--)
-    copy[i] = arr[i];
-  return copy;
+// As of node.js v5.4.1 (v8 v4.6.85.31) benchmarks showed, a simple for
+// loop performs better than Array#slice() for arrays smaller than 27
+// elements, it is worth it, because it's more likely to use EventEmitters
+// with a small number of listeners.
+function arrayClone(arr, length) {
+  if (length === 1) {
+    return [arr[0]];
+  }
+
+  if (length < 27) {
+    var copy = new Array(length);
+    for (var i = 0; i < length; i++)
+      copy[i] = arr[i];
+    return copy;
+  }
+
+  return arr.slice();
 }