A package for sort algorithms
Note that isSorted has a bit of an off-by-one error. It will check outside the bounds of its argument. This actually works OK, because it compares the last element of the array to undefined which always results in false. However, you should really only check up to index_outer &lt; length - 1.

I haven't looked too closely at your implementations of the basic sorting algorithms, but assuming they are correct, then there isn't much that could be said about their efficiency that hasn't already. It's all well defined.