Automatically call a function when accessing an object in Javascript

Question

I am currently on a big Javascript project with a lot of libraries. I would like to have some part of this project to run on separate thread. There is already something inJavascript doing that : the web workers.

Though, the web workers can't access the window object, and a lot of the libraries use it. Is there a way to automatically change the call to the window object (in the libraries used for the web workers), into a message sent to the parent thread ?

Then, the parent thread would perform the action that the worker want and send back the result to the worker.

Is it possible to do that ? And id yes, do you have any idea how ?

Thank you !

I am well aware of this function and it's sure I will use it to perform what I want to do. Though, what I am looking for is how to call this function automatically each time I want to access to the window object. — clementescolano
– clementescolano, Commented Jul 9, 2015 at 21:26

Community · Accepted Answer · 2017-05-23 11:43:51Z

1

I'm afraid there's no real solution to this. What you'd probably want is a special object in your worker, which, at every property access, passes the execution to the dispatching thread - which handles the request using the original window object.

To do this, you would need some sort of catch-all accessor method which would run whenever a property is referenced. Sadly, there's no such thing in Javascript, see this detailed discussion (especially T.J. Crowder's answer): Is it possible to implement dynamic getters/setters in JavaScript?

ECMAScript 6 introduces a new mechanism called Proxy (currently supported in FF and IE12 (go figure!)), which would enable you to do these dynamic property lookups, technically - but I feel there's a more fundamental problem with your idea: you're aiming to turn a local call into a message across the boundaries of single threaded environments.

Message passing from and to the worker threads must be asynchronous (as a javascript "thread" cannot be interrupted until it yields), which would mean that even if you do manage to set up a proxy like that, it'd be effectively turning a usually synchronous operation (ie. a property access) into an asynchronous one, which is a pretty big issue, especially if you're looking for a drop-in replacement in order to use some existing libraries.

edited May 23, 2017 at 11:43

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answered Jul 9, 2015 at 21:50

doldt

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1 Comment

clementescolano Over a year ago

Ok thank you for your answer and the links ! Well, I guess I will have to figure out another way then !

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