flagsmith-react

Flagsmith SDK for React Single Page Applications (SPA).

Contents

• Installation
• Getting Started
• API Reference

Installation

Using npm

npm install flagsmith-react

Using yarn

yarn add flagsmith-react

Getting Started

Configure the SDK by wrapping your application in a FlagsmithProvider element:

// src/index.js
import React from 'react';
import ReactDOM from 'react-dom';
import {FlagsmithProvider} from 'flagsmith-react';
import App from './App';

ReactDOM.render(
    <FlagsmithProvider
        environmentId="YOUR_FLAGSMITH_ENVIRONMENT_ID"
    >
        <App />
    </FlagsmithProvider>,
    document.getElementById('app')
);

The Flagsmith Provider defaults to using the vanilla JavaScript Flagsmith SDK. To support alternative SDK, for example the React Native variant, a specific provider can be supplied as a parameter, for example

// src/index.js
import React from 'react';
import ReactDOM from 'react-dom';
import {FlagsmithProvider} from 'flagsmith-react';
import flagsmith from 'react-native-flagsmith';
import App from './App';

ReactDOM.render(
    <FlagsmithProvider
        environmentId="YOUR_FLAGSMITH_ENVIRONMENT_ID"
        flagsmith={ flagsmith }
    >
        <App />
    </FlagsmithProvider>,
    document.getElementById('app')
);

Use the useFlagsmith hook in your components to access the Flagsmith state (isLoading, isIdentified, isError) and feature flag and remote configuration methods (hasFeature, getValue etc.)

import React from 'react';
import { useFlagsmith } from 'flagsmith-react';

function App() {
    const {
        isLoading,
        isError,
        hasFeature,
        getValue
    } = useFlagsmith();

    if (isLoading) {
        return <div>Flagsith state is loading...</div>
    }

    if (isError) {
        return <div>Failed to load Flagsmith state!</div>
    }

    const hasExtraText = hasFeature('extra_text')
    const theValue = getValue('example_value')

    return <div>
        <div>The value is {theValue}.</div>
        {
            hasExtraText && <div>Here is the extra text feature</div>
        }
    </div>
}

export default App;

API Reference

The flagsmith-react API is modelled on the Flagsmith Javascript integration, the documentation for which can be found here for further reference.

FlagsmithProvider

  <FlagsmithProvider 
    environmentId
    flagsmith
    asyncStorage
    cacheFlags
    defaultFlags
    preventFetch
    api>
  </FlagsmithProvider>

Use the FlagsmithProvider component to wrap your application and allow child elements to access the Flagsmith functionality using the 'useFlagsmith' hook function.

useFlagsmith

const {
    isLoading,
    isIdentified,
    isError,
    identify,
    hasFeature,
    getValue,
    subscribe
} = useFlagsmith();

Use the useFlagsmith hook in your components to access the Flagsmith state and methods.

isLoading: boolean

True if the Flagsmith state is loading, false is the state is loaded and usable. You should not try accessing the state (i.e. feature flags and remote configuration) until this is false and the state is loaded.

isIdentified: boolean

True if Flagsmith has been configured to use a specific identity when resolving flags and remote configuration, false otherwise.

See identify for more information.

isListening: boolean

True if Flagsmith is configured to listen for updates. See startListening for more details.

isError: boolean

True if the Flagsmith integration is in an errored state (e.g. the server could not be reached). False otherwise.

identify

await identify(identity)

Passes the supplied identity to the Flagsmith backend to be used when resolving feature flags and remote configuration. This causes an update in the state, which is an async action. Use the isIdentified flag to determine when the state has been re-loaded, or use subscribe to receive an update notification.

logout

await logout()

Remove any identity associated with the Flagsmith client. Use the isIdentified flag to determine when the state has been re-loaded, or use subscribe to receive an update notification.

hasFeature

hasFeature(key)

Determines is the feature specified key is set or not.

getValue

getValue(key)

Gets the current value of the remote configuration item specified by the key.

startListening

startListening(interval = 1000)

Begin listening for backend configuration changes. The polling interval is specified in mS. Use isListening to determine the current listening state, and subscribe to be notified of updates.

stopListening

stopListening()

Stop listening (polling) for configuration changes.

subscribe

subscribe(callback)

Registers a callback with Flagsmith that will be triggered any time a new configuration is available, for example after loading is complete, or when a new user is identified. This can be used to update any configuration state in components using Flagsmith, per the following example.

import { useEffect, useState } from 'react'
import logo from './logo.svg';
import './App.css';
import { useFlagsmith } from 'flagsmith-react'

function App() {
  const { isLoading, isError, getValue, identify, subscribe } = useFlagsmith()
  const [val, setVal] = useState()

  useEffect(() => {
    if(!isLoading) {
      identify('someone@somewhere.com')
    }
  }, [isLoading, identify])

  const handleChange = () => {
    setVal( getValue('val') )
  }

  subscribe(handleChange)

  return (
    <>
      {
        !isLoading &&
        <div className="App">
          <header className="App-header">
            <img src={logo} className="App-logo" alt="logo" />
            <p>
              Edit <code>src/App.js</code> and save to reload.
            </p>
            <a
              className="App-link"
              href="https://reactjs.org"
              target="_blank"
              rel="noopener noreferrer"
            >
              Learn React
            </a>
            {
              isError && <h3>Flagsmith failed to load</h3>
            }
            {
              val && <h1>{val}</h1>
            }
          </header>
        </div>
      }
    </>
  );
}

export default App;

getFlags

await getFlags()

Forces a fetch of the current flags.

getTrait

getTrait(key)

Can only be used once a user has been identified, to get the value of the specified trait for that user.

setTrait

await setTrait(key, value)

Can only be used once a user has been identified, to set the value of the specified trait for that user.

setTraits

await setTraits(traits)

Can only be used once a user has been identified, to set the value of the multiple traits for that user. Traits set to a value of null will be removed.

incrementTrait

await incrementTrait(key, incrementBy)

Can only be used once a user has been identified, used to increment (or decrement) the specified trait for that user.