code: function emitElement(element, name, onLeave) {
    if (Array.isArray(element)) {
      var i;
      for (i = 0; i < element.length - 1; i++) {
        emitOneElement.call(this, element[i], name);
      }
      emitOneElement.call(this, element[i], name, onLeave);
    } else {
      emitOneElement.call(this, element, name, onLeave);
    }
  }
docs: Emits a single element and its descendants, or an array of elements.