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Published Nov 4, 2023 ⦁ 7 min read

LaunchDarkly JavaScript SDK unveiled

Introduction

LaunchDarkly is a leading feature management platform that allows developers to control feature releases in their applications via feature flags. They recently announced the release of their new JavaScript SDK, which provides frontend developers an easy way to integrate LaunchDarkly and manage features on the client-side.

The key goals of the new SDK are to simplify integration, reduce bundle size, improve performance, and offer more flexibility for advanced use cases. With this latest version, developers can now tap into the full power of LaunchDarkly's platform through their JavaScript apps and websites.

Some of the major benefits of using LaunchDarkly's JS SDK include:

  • Easily toggling features on/off and targeting users
  • Gradual rollout and testing of new features
  • Reducing risk for development teams
  • Faster iteration without re-deploying
  • Powerful targeting and segmentation options
  • Enterprise-grade security and scalability

In this post, we'll take a deep dive into everything you need to know about the new LaunchDarkly JS SDK. We'll explore the key new capabilities, integration steps, usage examples, documentation resources, and more. Whether you're new to LaunchDarkly or looking to upgrade, you'll learn how to leverage the SDK to take control over your feature flags.

New Features

The latest LaunchDarkly JS SDK comes packed with several powerful new features to give developers more control and flexibility. Here are some of the most notable additions:

  • Smaller bundle size - The SDK bundle size is now significantly smaller, reduced by over 25% compared to previous versions. This results in faster page loads.

  • Async initialization - You can now initialize the SDK asynchronously to avoid blocking page load. This allows the SDK to be initialized after the DOM has loaded to prevent any blocking or delays in page rendering.

  • Observable flags - Flag values can be observed for changes instead of just fetching their current values. This enables reactive integrations where your UI can automatically update when flags change.

  • TypeScript support - The SDK now includes TypeScript definitions for better intellisense and static typing in TS projects.

  • Angular and React integrations - Specific wrappers are provided for simplified integration with Angular and React frameworks.

  • Server-side SDK compatibility - The client-side SDK has been aligned with server-side SDKs for a more unified and consistent experience.

Feature Flags

Feature flags are at the core of LaunchDarkly's offering. They allow you to toggle features on and off dynamically outside of code deployments. The JavaScript SDK makes it easy to check flag values and manage your flags from the frontend.

Here is a sample snippet for initializing the SDK and evaluating a feature flag:

const ldClient = LaunchDarkly.initialize("SDK_KEY", user)

const showFeature = ldClient.variation("show-widget", false)

if (showFeature) {
  // Show widget
} else {
  // Hide widget
}

Some best practices when working with feature flags in your JavaScript code:

  • Use meaningful flag keys like "show-widget" that describe the feature
  • Initialize flags to a default value for a fail-safe
  • Check flags on every page load instead of caching values
  • Target users gradually for rollout testing

The new SDK introduces more advanced targeting and rules capabilities for smarter flag evaluation. You can target based on custom user attributes, percentage rollouts, and advanced rules. Compared to a basic homegrown flag implementation, LaunchDarkly provides enterprise-level scalability, security, and reliability.

Framework Integrations

The LaunchDarkly SDK can be easily integrated into popular frontend frameworks like React, Angular, and Vue.

For React, you can initialize the SDK in your root component and then pass flags down via context or props:

// App.js

const ldClient = LaunchDarkly.initialize(...)

<FlagsProvider client={ldClient}>
  <MainApp />
</FlagsProvider>

// Feature.js

const { flags } = useContext(FlagsContext) 

{flags.showFeature && <Widget />}

For Angular, instantiate the SDK service in your app module. Components can inject and subscribe to flag values:

// app.module.ts

import { LDClient } from 'ldclient-js';

const ldClient = LDClient.initialize(...)

@NgModule({
  providers: [ ldClient ] 
})

The Vue plugin abstracts flag management through composables. Initialize the plugin once and then access flags via helpers in your components.

Build Tools

When using bundlers like Webpack and Rollup, you can import the LaunchDarkly SDK package directly:

import * as LaunchDarkly from 'ldclient-js'

For basic scripts, reference the SDK from a CDN:

<script src="https://unpkg.com/ldclient-js"></script>

The SDK integrates smoothly with all major build tools and bundlers including Parcel, Vite, and ESBuild.

Use Cases

LaunchDarkly's JavaScript SDK enables countless use cases through its flexible feature flag management. Here are some examples:

  • Progressive rollouts - Target a percentage of users to gradually test new features. For example, show a redesigned homepage to 10% of traffic.

  • A/B testing - Run experiments by delivering different variations of a feature to user segments. Test whether a new checkout flow improves conversion rates.

  • Kill switches - Quickly enable/disable features without re-deploying. Turn off a malfunctioning widget with one flag update.

  • User targeting - Customize experiences based on user attributes, platform, location, and more. Show premium content only to paid subscription members.

  • Access control - Restrict access to specific features based on custom rules and permissions. Grant admin capabilities only to authorized employee accounts.

The possibilities are endless! LaunchDarkly's SDK handles all the complexity so you can focus on building unique user experiences.

Comparing JavaScript SDKs

LaunchDarkly is one of several JavaScript SDKs available for managing feature flags and remote config. Some other popular options include:

  • Split.io
  • Flagr (open source)
  • Bullet Train
  • Unleash
  • Optimizely Rollouts

Compared to other SDKs, LaunchDarkly stands out in these areas:

  • Enterprise scalability - Proven at Fortune 100 customer scale
  • Advanced targeting - Fine-grained user segmentation
  • Robust platform - Integrations, CI/CD, custom workflows
  • Broad platform support - Mobile, web, backend, streaming
  • Performance and reliability - Speed and uptime

While open source options like Flagr offer flexibility, they lack the enterprise-level capabilities, support, and tooling integrations that LaunchDarkly provides.

Summary

The new LaunchDarkly JavaScript SDK provides a fast, flexible way to manage feature flags and remote config in your frontend applications. With its smaller footprint, reactive APIs, and framework integrations, it's now easier than ever to integrate LaunchDarkly into your JavaScript projects.

To get started, first review the SDK documentation and install the library. Initialize the client with your environment SDK key and start toggling feature flags!

Consider a free LaunchDarkly account to unlock enterprise capabilities as you scale, including fine-grained targeting, secure flag management, CI/CD integrations, custom workflows, and more.

With feature flags, you can deploy faster, reduce risk, toggle functionality, and create highly-customized user experiences. LaunchDarkly's new JS SDK provides the tools to make it happen!

LaunchDarkly JavaScript SDK unveiled

Introduction

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New Features

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Framework Integrations

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Use Cases

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Comparing JavaScript SDKs

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Summary

The new LaunchDarkly JavaScript SDK provides a fast, flexible way to manage feature flags and remote config in your frontend applications. With its smaller footprint, reactive APIs, and framework integrations, it's now easier than ever to integrate LaunchDarkly into your JavaScript projects.

To get started, first review the SDK documentation and install the library. Initialize the client with your environment SDK key and start toggling feature flags!

Consider a free LaunchDarkly account to unlock enterprise capabilities as you scale, including fine-grained targeting, secure flag management, CI/CD integrations, custom workflows, and more.

With feature flags, you can deploy faster, reduce risk, toggle functionality, and create highly-customized user experiences. LaunchDarkly's new JS SDK provides the tools to make it happen!

If you're looking for a platform to showcase your own developer tools and SDKs, check out DevHunt. DevHunt allows developers to easily list, launch and promote tools to the community.

Feature FlagsJavaScriptSDKs

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