Worker Threads in Javascript?

Does anyone know if it is possible to simulate worker threads in Javascript. I need a method of constantly polling a particular resource and dispatching events based on conditions in that resource.

Currently I am thinking that I will have to have methods triggered off timers. Is this acceptable?

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Wikipedia Documents

Javascript - Wikipedia, The Free Encyclopedia ,Ecmascript - Wikipedia, The Free Encyclopedia ,Wikipedia: Ajax ,Wikipedia: Thread (computer Science)