[2,1].sort(null) should throw TypeError

ECMA 15.4.4.11 Array.prototype.sort (comparefn)

Step 13:

If the argument comparefn is not undefined, then

    If IsCallable(comparefn) is false, throw a TypeError exception.

    Return the result of calling the [[Call]] internal method of comparefn passing undefined as the this value and with arguments x and y.