How to wrap or proxy another object in JavaScript in Node.js

Question

I'm doing JavaScript in node.js.

I'm trying wrap an object not yet constructed, allowing calls to any object function and set/get any object attribute through the wrapper, letting the wrapper pass calls/sets/gets to the object if bound in the wrapper or throw an exception if the object is not yet bound in the wrapper. I want to be ignorant to the object. I'm seeking a general purpose mechanism allowing me to wrap any object in this fashion.

I could construct a wrapper structure holding the object

wrapper = {
    object: SomeObject
};

and address the object through wrapper dereference

wrapper.object.someFunction();

but I want to be transparent and use the following syntax instead:

wrapper.someFunction();

I have looked into the Proxy features of ECMAScript 6 but constantly came short on the apply() function trap. Is there a problem with JavaScript V8 and Node.js not being ECMAScript 6 compliant.

Any ideas?

Community · Accepted Answer · 2017-05-23 11:43:39Z

0

What you want to do is to overload the "dot "operator, something very familiar to Python guys, the __getattr__ and __setattr__ functions.

Indeed, the way to do it in ECMAScript 6 is to use Proxies, and as this post says:

Proxies let you create objects that are true proxies (facades) for other objects

Javascript overloading dot

The problem is that NodeJS does not support ECMAScript 6.

So I see two solutions:

Why don't you do something a bit idiomatic like, have a function o that will return the object, that way you can do
```
wrapper.o().attribute = ...
```
Maybe try IO.js that supports ECMAScript 6 and is compatible with Node/npm?

edited May 23, 2017 at 11:43

CommunityBot

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answered May 5, 2015 at 23:00

Martin E. Zulliger

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