The end result is still O(n^2) in the number of vertices in the convex hull...
If you didn't just slap together JS libs, but studied the literature, you'd find that the proper algorithm for this problem runs in O(n) time, and is called the "rotating calipers" algorithm.
Some religious folks might find it a bit offensive. Thank you! (some alternatives: dang, darn, gosh, blimey, golly, etc.)