unleash-proxy-client

What is unleash-proxy-client?

The unleash-proxy-client npm package is a client library for the Unleash Proxy, which is a feature management system. It allows you to control feature toggles in your application, enabling or disabling features without deploying new code. This is particularly useful for A/B testing, gradual rollouts, and canary releases.

What are unleash-proxy-client's main functionalities?

Initialize Client

This code initializes the Unleash client with the necessary configuration such as the URL of the Unleash Proxy, the client key, and the application name. The `start` method is called to begin fetching feature toggles.

const { UnleashClient } = require('unleash-proxy-client');

const unleash = new UnleashClient({
  url: 'https://app.unleash-hosted.com/demo/api/frontend',
  clientKey: 'your-client-key',
  appName: 'my-app'
});

unleash.start();

Check Feature Toggle

This code checks if a specific feature toggle is enabled. The `isEnabled` method returns a boolean indicating the status of the feature toggle.

const isEnabled = unleash.isEnabled('feature-toggle-name');
console.log(`Feature is enabled: ${isEnabled}`);

Register Event Listeners

This code registers event listeners for the Unleash client. The `update` event is triggered when feature toggles are updated, and the `error` event is triggered if there is an error fetching feature toggles.

unleash.on('update', () => {
  console.log('Feature toggles updated');
});

unleash.on('error', (error) => {
  console.error('Error fetching feature toggles:', error);
});

Other packages similar to unleash-proxy-client

launchdarkly-node-client-sdk

LaunchDarkly is a feature management platform that allows you to control the release of features to users. It offers similar functionality to Unleash, such as feature toggles, A/B testing, and gradual rollouts. The main difference is that LaunchDarkly is a commercial product with more advanced analytics and targeting capabilities.

configcat-node

ConfigCat is a feature flag and configuration management service. It provides similar functionalities to Unleash, including feature toggles and remote configuration. ConfigCat is known for its simplicity and ease of use, making it a good alternative for smaller projects or teams.

flagr

Flagr is an open-source feature flagging and A/B testing service. It allows you to create and manage feature flags and run experiments. Flagr is similar to Unleash in that it is open-source and can be self-hosted, but it also includes built-in support for A/B testing and experimentation.

README

Unleash Proxy Client for the browser (js)

This is a tiny Unleash Client SDK you can use together with the Unleash Proxy. This makes it super simple to use Unleash from any single page app.

This client expect fetch to be available. If you need to support older browsers you should probably use the fetch polyfill.

Frameworks supported

This package is not tied to any framework, but can be used together most popular frameworks, examples:

• Unleash React SDK
• React
• React Native
• Angular JS
• Vue.js
• ...and probably your favorite!

How to use the client as a module.

Step 1: Install

npm install unleash-proxy-client --save

Step 2: Initialize the SDK You need to have a Unleash-hosted instance, and the proxy need to be enabled. In addition you will need a proxy-specific clientKey in order to connect to the Unleash-hosted Proxy.

import { UnleashClient } from 'unleash-proxy-client';

const unleash = new UnleashClient({
    url: 'https://eu.unleash-hosted.com/hosted/proxy',
    clientKey: 'your-proxy-key',
    appName: 'my-webapp'
});

// Used to set the context fields, shared with the Unleash Proxy
unleash.updateContext({userId: '1233'});

// Start the background polling
unleash.start();

Step 3: Check if feature toggle is enabled

unleash.isEnabled('proxy.demo');

Step 4: Get toggle variant

const variant = unleash.getVariant('proxy.demo');
if(variant.name === 'blue') {
 // something with variant blue...
}

Listen for updates via the EventEmitter The client is also an event emitter. This means that your code can subscribe to updates from the client. This is a neat way to update a single page app when toggle state updates.

unleash.on('update', () => {
    const myToggle = unleash.isEnabled('proxy.demo');
    //do something useful
});

SessionId - Important note!

You may provide a custom session id via the "context". If you do not provide a sessionId this SDK will create a random session id, which will also be stored in the provided storage (local storage). By always having a consistent sessionId available ensures that even "anonymous" users will get a consistent experience when feature toggles is evaluated, in combination with a gradual (percentage based) rollout.

Custom store

This SDK will use @react-native-async-storage/async-storage to backup feature toggles locally. This is useful for bootstrapping the SDK the next time the user comes back to your application.

You can provide your own storage implementation.

Example:

import SharedPreferences from 'react-native-shared-preferences';
import { UnleashClient } from 'unleash-proxy-client';

const unleash = new UnleashClient({
    url: 'https://eu.unleash-hosted.com/hosted/proxy',
    clientKey: 'your-proxy-key',
    appName: 'my-webapp',
	storage: {
		save: (name: string, data: any) => SharedPreferences.setItem(name, data),
		get: (name: string) => SharedPreferences.getItem(name, (val) => val)
	},
});

How to use in node.js

This SDK can also be used in node.js applications (from v1.4.0). Please note that you will need to provide a valid "fetch" implementation. Only ECMAScript modules is exported from this package.

import fetch from 'node-fetch';
import { UnleashClient, InMemoryStorageProvider } from 'unleash-proxy-client';

const unleash = new UnleashClient({
  url: 'https://app.unleash-hosted.com/demo/proxy',
  clientKey: 'proxy-123',
  appName: 'nodejs-proxy',
  storageProvider: new InMemoryStorageProvider(),
  fetch,
});

await unleash.start();
const isEnabled = unleash.isEnabled('proxy.demo');
console.log(isEnabled);

index.mjs

How to use the client via CDN.

<html>
<head>
    <script src="https://unpkg.com/unleash-proxy-client@latest/build/main.min.js" type="text/javascript"></script>
    <script type="text/javascript">
        var config = {url: 'https://app.unleash-hosted.com/demo/proxy', clientKey: 'proxy-123', appName: 'web'};
        var client = new unleash.UnleashClient(config);
        client.updateContext({userId: '1233'})

        client.on('update', () => {
            console.log(client.isEnabled('proxy.demo'));
        });
        client.start();
    </script>
</head>
</html>