This is a library which enables users to "trap" deeply nested objects into proxies. The API is identical to the proxy API, except that traps get an additional this context with a method for nesting the current proxied object into a deeper one.

✨ Now updated with support for TypeScript! See the change log for more information.

🚀 All external dependencies have been stripped, making this library self-contained!

Examples

A simple example for DSL query building:

const DeepProxy = require('proxy-deep');

const db = new DeepProxy({}, {
  get(target, path, receiver) {
    return this.nest(function () {})
  },
  apply(target, thisArg, argList) {
    return this.path;
  }
})

console.log(db.select.from.where()) // outputs ['select', 'from', 'where']

Another example using Node's process object:

const DeepProxy = require('proxy-deep')
const { EventEmitter } = require('events')

const emitter = new EventEmitter()

const pp = DeepProxy(process, {
  get(target, key, receiver) {
    const val = Reflect.get(target, key, receiver);
    if (typeof val === 'object' && val !== null) {
      return this.nest({})
    } else {
      emitter.emit('access', this.path)
      return val
    }
  }
})

emitter.on('access', path => {
  console.log(`${path} was accessed.`)
})

pp.argv[0] // trapped!

API

import DeepProxy from "proxy-deep"

import { DeepProxy, TrapThisArgument, DeepProxyHandler } from "proxy-deep"

TrapThisArgument<T>

A TypeScript type that holds all information about the this argument inside a proxy trap.

To speed things up, the same this-argument is shared between calls to different traps. You should not make use of this implementation detail, and instead pass any information you wish to share in a custom object inside options.userData.

new DeepProxy(target, handlers, [options])

Identical to new Proxy(target, handlers), except that the callbacks provided in the traps object will be called wiith a this-context that has some additional properties. For a full reference on what arguments are provided to the handlers, please consult the a MDN web docs.

options is an object that can contain the following entries:

• path either a string denoting the full path to the object or an array of property keys
• userData an object of which the enumerable properties will be copied to the this-argument of a proxy trap handler

this.rootTarget

A reference to the object with wich the deep proxy was created.

this.path

Holds the full property path to the given object.

this.nest([nestedTarget])

Returns a new proxy that will trap methods as described in this API. nestedTarget is an optional object with which the proxy will be initialized. If it is not specified, the target that was passed to new DeepProxy() will be used.

handler.getPrototypeOf()

A trap for Object.getPrototypeOf.

handler.setPrototypeOf()

A trap for Object.setPrototypeOf.

handler.isExtensible()

A trap for Object.isExtensible.

handler.preventExtensions()

A trap for Object.preventExtensions.

handler.getOwnPropertyDescriptor()

A trap for Object.getOwnPropertyDescriptor.

handler.defineProperty()

A trap for Object.defineProperty.

handler.has()

A trap for the in operator.

handler.get()

A trap for getting property values.

handler.set()

A trap for setting property values.

handler.deleteProperty()

A trap for the delete operator.

handler.ownKeys()

A trap for Object.getOwnPropertyNames and Object.getOwnPropertySymbols.

handler.apply()

A trap for a function call.

handler.construct()

A trap for the new operator.

FAQ

I get an error foo is not a function!

You must pass a fuction as the object to be proxied if you want traps.apply to work, like so:

const proxy = new DeepProxy(function () {}, {
    apply() {
        return 42;
    }
});

License

The MIT License