ProxyScope

Bootstrap for combining object be reference with ES proxy, and reusing them on other proxy-factories. Which will also reflect changes made to the original objects. Proxies can also be useful when using immutables or mixins.

Caution this method uses Proxies and therefor will only work in modern enviroments. Please view CanIUse for more information.

Install

npm i @aboutweb/proxyscope

ProxyFactory(`...(traps || factory))

traps chain of traps merged for the new Proxy

factory a previous created factory

returns a factory function with a traps property

factory(Object target | Array<Object target>, ...traps)

target an object or array of object to use as stack for lookups

traps to combine while creating a new proxy

Example

import { default as proxyFactory } from "@aboutweb/proxyscope";
import otherFactory from "./otherfactory.js";

const traps = {
  has(target, property, receiver) {
    return this.findHost(property);
  },
  /*helper method*/
  findHost(property, root) {
    let host = this.stack.find(function(level) {
      return property in level;
    });

    if(host) {
      return host;
    }

    if(root === true) {
      return this.stack[0];
    }
  }
}

const factory = proxyFactory(traps, otherfactory);

export {
  factory as default,
  traps
}

ProxyScope.read

Uses the target.stack to look up properties.

Example

import { read as proxyRead } from "@aboutweb/proxyscope";

let defaultConfig = {
  fu : "bar"
}

function someFn(config) {
  let proxy = proxyRead(config, defaultConfig);

  expect(proxy.fu).to.equal("bar");
  expect(proxy.bar).to.equal("baz");
}

someFn({
  bar : "baz"
});

ProxyScope.write

same as proxyRead but will also forward writes if they are defined somewhere in the level chain.

Example

const l1 = {
  some : "value"
}

const l2 = {
  fu : "bar"
}

let proxy = proxyWrite(l1, l2);

proxy.fu = "hallo";

expect(l2.fu).to.equal("hallo");

ProxyScope.readDeep

read even nested objects, extends proxy-read by returning a new proxy for every property that has multiple possible getters

Use wisely, because this will create a proxy for every property lookup that has more then one possible value. Therefor it is recommended to cache lookups when possible.

Example

import { readDeep as proxyReadDeep } from "@aboutweb/proxyscope";

const l1 = {
  nested : {
    some : "value",
  }
}

const l2 = {
  nested : {
    fu : "bar"
  }
}

const l3 = {
  other : true
}

let proxy = proxyReadDeep(l1, l2, l3);

//before caching or update cache afterwords
l3.nested = {
  deep : true
}

//cache the returned proxy
let nested = proxy.nested;

expect(nested.some).to.equal("value");
expect(nested.fu).to.equal("bar");
expect(nested.deep).to.equal(true);

ProxyScope.writeDeep

same as proxyReadDeep, but will also write to nested objects

Example

import { writeDeep as proxyWriteDeep } from "@aboutweb/proxyscope";

const l1 = {
  nested : {
    some : "value",
  }
}

const l2 = {
  nested : {
    fu : "bar"
  }
}

let proxy = proxyReadDeep(l1, l2);

//also use cache where possible
let nested = proxy.nested;

nested.some = "other";
nested.fu = "baz";

expect(l1.nested.some).to.equal("other");
expect(l2.nested.fu).to.equal("baz");

Licence

ISC