ECMAScript 6 proxies fun (method missing, negative array indexes)

method-missing.coffee

# Ruby’s “method missing” analog with ES6 proxies.
proxify = (object) ->
  new Proxy object, get: (receiver, name) ->
    object[name] ? object.methodMissing.bind object, name

object = proxify
  a: 1,
  b: 15,
  c: ->
    'called'
  methodMissing: (name, args...) ->
    console.log "Calling missing method #{name} with arguments", args

console.log 'Accessing property "a":', object.a
console.log 'Accessing property "b":', object.b
console.log 'Calling method "c":', object.c()
object.methodName 1, 2, 3, 4

negative-array-indexes.coffee

# Negative array indexes with ES6 direct proxies.
enableNegativeIndexes = (array) ->
  new Proxy array, get: (receiver, name) ->
    console.log 'Proxy#get', array, name
    index = parseInt name
    if not isNaN(index) and index < 0
      array[array.length + index] 
    else 
      array[name]

# array = enableNegativeIndexes [100, 500, 600]
# array[-1] is 600
# => true

have you tried this in an application?!? it is sure interesting but how expensive is it to wrap objects in a proxy!??

Just benchmarked this. Performance of proxies sucks: http://jsperf.com/proxy-cost.

The slowdown is x1000.

not good… did you find another solution to emulate it?!?

…

On 2012-03-18, at 22:40 , Paul Miller wrote: Just benchmarked this. Performance of proxies sucks: http://jsperf.com/proxy-cost. The slowdown is x1000. --- Reply to this email directly or view it on GitHub: https://gist.github.com/1648257

Sadly, no. Firefox has __noSuchMethod__ but it's non-standard.

yes and it doesn't work with nodejs since that uses v8 :(