Comparision of a Normal Merge Sort and Distributed Merge Sort is used.

Normal Merge Sort: It is done in the main thread (the only thread) , basic implementaion of merge sort.

Distributed Merge Sort: It is done in the worker threads, by using at max 4 worker threads at a time. Merge Sorting 1/4 of part array in different workers. Then merging the 4 parts, in two different workers by making it parallel. Thereby speeding it up.
Using SharedArrayBuffer, we can easily send reference to the worker threads without the overhead of copying over. Combining Web Workers and SharedArrayBuffer,We can implement a lot of parallel algorithms, achieve speed which was possible in low level languages. Also read, TypedArrays which makes numerical arrays creation superfast.