Collections.addAll(all, others);
    return copyOf(all.iterator());
  }

  /** ImmutableSet.of API that is friendly to use from JavaScript. */
  @JsMethod(name = "of")
  static <E> ImmutableSet<E> jsOf(E... elements) {
    return copyOf(elements);
  }

  @JsMethod
  public static <E> ImmutableSet<E> copyOf(E[] elements) {
    checkNotNull(elements);
    switch (elements.length) {
      case 0: