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0.7.1 • Public • Published


Declarative feature flags in React using Appknobs.io

Appknobs.io is an easy & ergonomic feature flag solution for your web & mobile apps, including modern libraries, management console, config delivery & CLI tools.

This package contains the React helper components.


Add @appknobs/react and @appknobs/client as a dependency:

For NPM:

npm install @appknobs/react @appknobs/client
// or
yarn add @appknobs/react @appknobs/client

The @appknobs/client README has a few hints on performance and bundle size


React versions

For React 16.3.0 and above use the top level @appknobs/react modules:

import {Appknobs, Feature} from '@appknobs/react'
// or
const {Appknobs, Feature} = require('@appknobs/react')

For React 15.0.0+ use @appknobs/react/lib/legacy:

import {Appknobs, Feature} from '@appknobs/react/lib/legacy'
// or
const {Appknobs, Feature} = require('@appknobs/react/lib/legacy')

Browser only example

The simplest way to make a feature manageable by Appknobs is to wrap it in a <Feature> tag.

import * as React from 'react'
import {render} from 'react-dom'
import {Appknobs, Feature} from '@appknobs/react'
import {newBrowserClient} from '@appknobs/client'
// for smaller client bundle size you can use
// import {newBrowserClient} from '@appknobs/client/lib/newBrowserClient'
class App extends React.Component {
   public render() {
    return (
      <Appknobs client={this.props.client} payload={{email: 'foo@example.com'}}>
          <Feature name='first-feature'>
            <p>This feature is hidden behind a feature toggle!</p>
const client = newBrowserClient({apiKey: 'YOUR_API_KEY', appId: 'YOUR_APP_ID'})
render(<App client={client} />, document.querySelector('#root'))

If you use @appknobs/cli for feature discovery, the feature name must be a string literal and not a variable.

For performance reasons we recommend using render props though - see below

See the "Application Setup" section for getting your appId and apiKey

Function as children aka render props

<Feature> supports the technique called render props allowing you to implement any custom rendering logic. It is especially useful in the following cases:

Prevent mounting the child component

Components wrapped in <Feature> are still mounted. To prevent this, you can use a similar condition to avoid performance penalty or unwanted side effects:

  render={(enabled) => enabled && <Cats />)}

Wrapping breaks styling

Some libraries dictate strict component hierarchy hence you can't directly wrap components in <Feature>. One solution to this problem is the following:

<Feature name='cats' render={(enabled) => (
    {enabled && <Menu.Item>Cats</Menu.Item>}
)} />

Server-side Rendering (SSR) example

import {Feature, withAppknobs} from '@appknobs/react'
import {newNodeClient} from '@appknobs/client'
server.get('/', async (req, res) => {
    const payload = {environment: 'QA'}
    const client = newNodeClient({apiKey: 'YOUR API KEY', appId: 'YOUR APP ID'})
    const {features} = await client.evaluate(payload)
    const App = withAppknobs(client, features)(MyApp)
    const markup = renderToString(<App />)
      `<!doctype html>
    <html lang="">
          <title>Appknobs Example</title>

React Native & Electron

Besides Node and browsers, @appknobs/client supports React Native and Electron runtimes too so the <Appknobs>, <Feature> and other modules work as expected. For more details, check out @appknobs/client

Application Setup

To take advantage of the Appknobs ecosystem, you will need to

  • Register a user
  • Grab an API key
  • Register one or more applications (website or mobile app).

You can either use the Appknobs web Console or the @appknobs/cli CLI tool.

To use the Console, visit http://console.appknobs.io/.

To use the CLI tool, install it with

npm install -g @appknobs/react
// or
yarn global add @appknobs/react

Register a user

You can register online or inside your project folder run

knobs register

You will be asked for an email address and a password. Note your API key.

Parse your codebase

Let Appknobs look up the feature flags in your codebase and register an app for you, e.g.:

knobs parse src/

Example output, assuming you've implemented two <Feature> components:

App name: my-shop
App ID: H~6Jil_RTt~PT2BGjR~ZU
Found the following flags:
👉 new-section
👉 delete-button
Saving flags...
👍 new-section saved
👍 delete-button saved

You will need to copy-paste the App ID seen above to the Appknobs client implementation, so for the above example:

const appknobsClient = newClient({apiKey: 'ASDJI1mY3uW29bO50MA2q', appId: 'H~6Jil_RTt~PT2BGjR~ZU'})

Your app name will be picked up from package.json and this is only for your reference.

Feature management

You'll now be able to log in with your username and password and see your apps and corresponding feature flags on the web console:



The rules for enabling or disabling certain feature flags can be set using conditions.

Conditions are evaluated based on two things:

  • the payload coming from your client-side code
  • the conditions you set on the console that must be true for the feature to be enabled

Simple example


Consider the following basic feature flag:

<Feature name='foo'>

Note: features are disabled by default.


Imagine a simple condition, with the following, single rule:

Property: email

Predicate: startsWith

Argument: foo


Now, assuming your client-side code sends the following payload using @appknobs/react:

await client.evaluate({email: 'foo@example.com'})

the feature will be enabled, while in the following case

await client.evaluate({email: 'bar@example.com'})

the feature will not be visible to the end user.

Visit https://console.appknobs.io/ to implement your own use cases.

We appreciate your feedback! Get in touch at hello@appknobs.io or @appknobs


npm i @appknobs/react

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