[imtringued]

You can only send strings to webworkers in javascript. Without shared memory you have to send a serialised copy of your data to the other process which then has to deserialise it. In most cases this is perfectly fine. But if you have a lot of data then moving it around might take more time than the computation itself. In this case you're forced to use shared memory.

[dchest]

Not true, you can send ArrayBuffers to webworkers as transferable objects without copying: https://developers.google.com/web/updates/2011/12/Transferab...