4 ms·

This is a great article. Proxies really have gotten lost in the hype around ES6. Surely it's in part because JS developers have obvious pain points with async c

by cjhveal 10y ago

This is a great article. Proxies really have gotten lost in the hype around ES6. Surely it's in part because JS developers have obvious pain points with async control flow and clumsy syntax, so things like generators and generous helpings of syntactic sugar are the most visible changes. However, I'm inclined to think that the level of abstraction and the complex API make it difficult for many developers to recognize their use cases or even play around with them.

spion 10y ago
Its because proxies are too hard to compile to ES5. Every function call, array access, property access etc is potentially going to end up calling a proxy, and as such will have to be compiled to impossible-to-read code. Also, all of the examples given there can be implemented more elegantly using decorators. The more useful cases are dynamically generated method names (e.g. for ORMs) and array index access (e.g. MobX) for non-array datastructures, both of which could've been handled with a less invasive language feature...
- jannes 10y ago
  What do you think about immutable data structures as a use case? (e.g. https://facebook.github.io/immutable-js/ https://facebook.github.io/immutable-js/)
- qwertyuiop924 10y ago
  On the contrary, I can think of tons of uses for proxies, from Ruby-style MethodMissing, to object.observe functionality.
  - brycepj 10y ago
    Love those ideas.
  - spion 10y ago
    For a dynamic set of properties, an observable dictionary is better. For a fixed and known set of properties, its possible to enumerate them with "@observable" decorators beforehand (e.g. see MobX) Method missing is an alternative to proxies, not a feature. IMO, a lot of use cases for proxies are mistakes and/or better handled without them.
    - qwertyuiop924 10y ago
      What? No. MethodMissing is far more limited than proxies. Proxies are effectively a far more complex version of Python's properties. @observable isn't part of the language, and indeed may use proxies under the surface.
      - spion 10y ago
        Yes, method missing is a far more limited alternative to proxies. But its not a use case for proxies, they just have intersecting sets of use cases. It doesn't make sense to "just" implement method_missing, you would do that so that you can implement other things on top of method_missing. @observable does not need proxies. Only implementing operator[] does. Which also could've been done with a far more limited feature, namely adding a symbol for the [] method. Proxies are just silly.
- wrong_variable 10y ago
  I didn't read the username but then saw 'MobX' and went 'wait a minute'

by cjhveal 10y ago

spion 10y ago

Its because proxies are too hard to compile to ES5. Every function call, array access, property access etc is potentially going to end up calling a proxy, and as such will have to be compiled to impossible-to-read code. Also, all of the examples given there can be implemented more elegantly using decorators. The more useful cases are dynamically generated method names (e.g. for ORMs) and array index access (e.g. MobX) for non-array datastructures, both of which could've been handled with a less invasive language feature...

jannes 10y ago
What do you think about immutable data structures as a use case? (e.g. https://facebook.github.io/immutable-js/ https://facebook.github.io/immutable-js/)
qwertyuiop924 10y ago
On the contrary, I can think of tons of uses for proxies, from Ruby-style MethodMissing, to object.observe functionality.
- brycepj 10y ago
  Love those ideas.
- spion 10y ago
  For a dynamic set of properties, an observable dictionary is better. For a fixed and known set of properties, its possible to enumerate them with "@observable" decorators beforehand (e.g. see MobX) Method missing is an alternative to proxies, not a feature. IMO, a lot of use cases for proxies are mistakes and/or better handled without them.
  - qwertyuiop924 10y ago
    What? No. MethodMissing is far more limited than proxies. Proxies are effectively a far more complex version of Python's properties. @observable isn't part of the language, and indeed may use proxies under the surface.
    - spion 10y ago
      Yes, method missing is a far more limited alternative to proxies. But its not a use case for proxies, they just have intersecting sets of use cases. It doesn't make sense to "just" implement method_missing, you would do that so that you can implement other things on top of method_missing. @observable does not need proxies. Only implementing operator[] does. Which also could've been done with a far more limited feature, namely adding a symbol for the [] method. Proxies are just silly.
wrong_variable 10y ago
I didn't read the username but then saw 'MobX' and went 'wait a minute'