Proxy - handler.ownKeys() - nested object

Question

How can I handle all traps for ownKeys in a nested object?

I only know how to handle one level deep object:

function wrap(obj, fn) {
  var handler = {
    ownKeys(target) {
      fn(target)
      return target
    }
  }
  return new Proxy(obj, handler)
}

var origObj = {
  a: {
    b: {
     c: 0
    }
  }
}

var wrappedObj = wrap(origObj, console.log)

Object.keys(wrappedObj) // => actual = expected: { a: { b: { c: 0 } } }
Object.keys(wrappedObj.a) // => actual: not working, expected: { b: { c: 0 } }
Object.keys(wrappedObj.a.b) // => actual: not working, expected: { c: 0 }

edit 1:

If I try to wrap each inner object (from this answer) then it logs all steps not just the last one. By "all steps" I mean the inner process of the proxy which goes through the whole nested object so it fires fn(target) multiple times but I want to fire it only once.

edit 2:

So it looks that the problem is with the node environmnent (node version 8.1.4) where proxy looks broken. In the chrome console is everything ok.

Yes, I know that's why I asked how can I do that for nested object (sry for my english). — Matej Mazur
– Matej Mazur, Commented Aug 31, 2017 at 7:01
If you don't want to create proxies recursively, you need to traverse the target inside the proxy. — user6445533
– user6445533, Commented Aug 31, 2017 at 8:43

Bergi · Accepted Answer · 2017-08-31 09:30:28Z

1

You have to create a proxy for every single of the objects:

var wrappedObj = wrap({
  a: wrap({
    b: wrap({
     c: 0
    }, console.log)
  }, console.log)
}, console.log)

If you don't want to do that explicitly, you can of course also traverse the object using recursion to do the wrapping programmatically, or you do create the proxies dynamically on every property access via the get trap.

answered Aug 31, 2017 at 9:30

Bergi

671k162 gold badges1k silver badges1.5k bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Matej Mazur Over a year ago

This doesn't work because it logs all steps not just the last one.

Bergi Over a year ago

@MatejMazur What do you mean by "just the last one"? I thought you wanted each of the three Object.keys calls to trigger the log.

Matej Mazur Over a year ago

I've updated my question with the screenshot of the console where it's visible the output.

Bergi Over a year ago

@MatejMazur Ah, I see now. That seems to be a problem with your console - the console.log itself does enumerate the contents of the logged object, triggering its trap again. Try in another environment or with a different callback function. (It shows as expected in Chrome devtools for example)

Matej Mazur Over a year ago

I see! Interesting.. thanks for the clarification! :)

Collectives™ on Stack Overflow

Proxy - handler.ownKeys() - nested object

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related