Proxy Polyfill

Proxy object polyfill
Alternatives To Proxy Polyfill
Project NameStarsDownloadsRepos Using ThisPackages Using ThisMost Recent CommitTotal ReleasesLatest ReleaseOpen IssuesLicenseLanguage
Proxy Polyfill1,0913962069 months ago11July 01, 20204apache-2.0JavaScript
Proxy object polyfill
Ajax Include Pattern63013a year ago2July 18, 2016mitJavaScript
An Ajax-Include Pattern for Modular Content
Serviceworker Polyfill66
9 years ago14JavaScript
[DEPRECATED] JavaScript ServiceWorker implementation, enabling exploration by authors.
Localstorage Polyfill5828477 years ago5September 14, 2016mitJavaScript
in memory localStorage polyfill for node.js utilizing ES6 proxies
Custom Elements Hmr Polyfill43232 years ago14July 11, 20201mitTypeScript
Custom Elements HMR polyfill
Es6 Proxy Polyfill39372 years ago7April 13, 20212apache-2.0JavaScript
ES6 Proxy polyfill, supports IE8+, Node.js, etc.
10 years ago9JavaScript
A prollyfill for ES6 typed/structured objects
a year ago1mitJavaScript
composable, reactive dom elements with sparse rendering
Pimped Proxy5
6 years ago3June 01, 2017TypeScript
Comprehensive and simple Proxy implementation for ECMAScript
Ee Proxy5
4 years ago10September 19, 20191mitJavaScript
Event emitter proxy for easy local listeners cleanup
Alternatives To Proxy Polyfill
Select To Compare

Alternative Project Comparisons

Please note that this polyfill is now in maintenance mode, as of Jan, 2023. We are not planning to add more features or enhancements.

This is a polyfill for the Proxy object, part of ES6. See the MDN docs or Introducing ES2015 Proxies for more information on Proxy itself. Unlike other polyfills, this does not require Object.observe, which is no longer supported anywhere.

⚠️ Note that Firefox, Chrome, Safari 10+ and Edge support Proxy natively. You don't need this if you're only targeting these modern browsers.

The polyfill supports just a limited number of proxy 'traps'. It also works by calling seal on the object passed to Proxy. This means that the properties you want to proxy must be known at creation time.

Additionally, your objects' prototypes will be snapshotted at the time a proxy is created. The properties of your objects can still change - you're just unable to define new ones. For example, proxying unrestricted dictionaries is not a good use-case for this polyfill.

Currently, the following traps are supported-

  • get
  • set
  • apply
  • construct

The Proxy.revocable method is also supported, but only for calls to the above traps.

This has no external dependencies. Skip down to usage to get started.


The most compelling use case for Proxy is to provide change notifications.

function observe(o, callback) {
  return new Proxy(o, {
    set(target, property, value) {
      callback(property, value);
      target[property] = value;

const x = {'name': 'BB-8'};
const p = observe(x, (property, value) =>, value)); = 'BB-9';
// name BB-9

You can extend this to generate change notifications for anywhere in an object tree-

function observe(o, callback) {
  function buildProxy(prefix, o) {
    return new Proxy(o, {
      set(target, property, value) {
        // same as above, but add prefix
        callback(prefix + property, value);
        target[property] = value;
      get(target, property) {
        // return a new proxy if possible, add to prefix
        const out = target[property];
        if (out instanceof Object) {
          return buildProxy(prefix + property + '.', out);
        return out;  // primitive, ignore

  return buildProxy('', o);

const x = {'model': {name: 'LEAF'}};
const p = observe(x, (property, value) =>, value)); = 'Tesla';
// Tesla

Adding new properties

The following line will fail (with a TypeError in strict mode) with the polyfill, as it's unable to intercept new properties-

p.model.year = 2016;  // error in polyfill

However, you can replace the entire object at once - once you access it again, your code will see the proxied version.

p.model = {name: 'Falcon', year: 2016};
// model Object {name: "Falcon", year: 2016}

For a similar reason, this polyfill can't proxy Array objects very well - but you can replace them all at once.


Install via your favourite package manager as proxy-polyfill.

To polyfill Proxy everywhere

You should either:

  • include proxy-polyfill into your build system (just require it directly, it doesn't export anything), or
  • import the proxy.min.js file directly.

This is the recommended approach and works on the web, in Node, or React Native.

Do not import ./src/proxy.js in old browsers directly, as it uses modern JavaScript features. It needs to be compiled, which is why we have the proxy.min.js file.

To consume the polyfill as a function

This is an advanced pattern. Requires ./src/proxy.js, which exports a proxy polyfill builder function in commonJS.

// commonJS require
const proxyPolyfill = require('proxy-polyfill/src/proxy')();

// Your environment may also support transparent rewriting of commonJS to ES6:
import ProxyPolyfillBuilder from 'proxy-polyfill/src/proxy';
const proxyPolyfill = ProxyPolyfillBuilder();

// Then use...
const myProxy = new proxyPolyfill(...);


The polyfill supports browsers that implement the full ES5 spec, such as IE9+ and Safari 6+. It may work in other non-browser environments too.

Popular Polyfill Projects
Popular Proxy Projects
Popular Libraries Categories
Related Searches

Get A Weekly Email With Trending Projects For These Categories
No Spam. Unsubscribe easily at any time.