[z3t4]

This is a very nice article! There's however a bug in the code, where it will "finish" when the last worker is done:

  if(msg.data.offset + msg.data.length === buffer.byteLength)

While you most likely want to wait for all workers to be done before showing the results. In this code however, the last worker will always finish last because it has more work to do (higher numbers).

It's often cheaper to scale horizontally, by spreading the work between physical machines, then to add more cores to a shared memory. So it's not such a big deal to have a single threaded program, and single threaded code is easier to reason about. SharedArrayBuffer will however be nice in JavaScript because it allows optimization is games and such, allowing you to have parallel for loops.