task.js

Well for one workers do not share scope, and at the moment sharing memory between the two is quite difficult. Second is race conditions like @btilly explained. Right now workers are mainly used for extreme situations and eventually make it into libraries that others use. I have created a library called Task.js that surfaces this idea into a promise compatible interface where you can just convert a pure function into a worker function. The end result is a promise supported function thats sends the function to a worker with your provided args and resolves when its done (also supports multiple workers and automatic queuing). https://github.com/icodeforlove/task.js

I kept finding myself needing to toss stuff in a background thread, and ended up making this: https://github.com/icodeforlove/task.js It makes wrangling multiple workers much easier, and doesn't require you to have external JS files. (also works in node.js) demo: http://s.codepen.io/icodeforlove/debug/ZOjBBB/NjrYzwzWdzLA