proxy-handler

Proxy object handler implementation.

Install

npm install proxy-handler

Usage

The Handler class redirects to a source object by default for all handler methods. You can extend the Handler class or select certain calls to be disabled.

new Handler(source: () => object, options?: object)

• source: a getter function returning the object to wrap to be run on each property access, unless memoized.
• options: an object with optional fields:
  • memoize: boolean, whether to memoize the source function.
  • disable: object, with optional keys of the methods to be disabled (getPrototypeOf, setPrototypeOf, has, get, set, etc) and boolean values.

As a verbose example without deselecting any methods:

import { Handler } from 'proxy-handler';

let item = { foo: 'foo' };
const handler = new Handler(() => item);
const wrap = new Proxy({}, handler);

console.log(wrap.foo); // 'foo'

wrap.foo = 'bar';
console.log(wrap.foo); // 'bar'
console.log(item.foo); // 'bar'

item = { foo: 'baz' };
console.log(wrap.foo); // 'baz'

We can also make the source getter run once, when the first property is accessed:

import { Handler } from 'proxy-handler';

const handler = new Handler(() => ({}), { memoize: true });

Or disable certain methods:

import { Handler } from 'proxy-handler';

const item = { foo: 'foo' };
const handler = new Handler(() => item, { disable: { set: true } });
const wrap = new Proxy({}, handler);

wrap.foo = 'bar';
console.log(wrap.foo); // 'foo'

Handler.proxy(source: () => object, options?: object)

We can achieve the same with Handler.proxy, which will return directly the proxy object, making it a little less verbose.

import { Handler } from 'proxy-handler';

const item = { foo: 'foo' };
const wrap = Handler.proxy(() => item);

console.log(wrap.foo); // 'foo'