code: function sortExternal(array, customCompare) {
    var compare = wrapCompare(customCompare, sortExternal.compareObserver);
    var swap = attachObserver(defaultSwap, sortExternal.swapObserver);
    return sort(array, 0, array.length - 1, compare, swap);
  }
docs: Sorts an array using quicksort.
  @param {Array} array The array to sort.
  @param {function} customCompare A custom compare function.
  @returns The sorted array.