launchdarkly-js-sdk-common

What is launchdarkly-js-sdk-common?

The launchdarkly-js-sdk-common package is a JavaScript SDK for LaunchDarkly, a feature management platform that allows developers to control the release of features to users. This SDK provides the core functionality for interacting with LaunchDarkly's feature flagging and experimentation capabilities.

What are launchdarkly-js-sdk-common's main functionalities?

Initialize the SDK

This feature allows you to initialize the LaunchDarkly client with your environment key and user information. The client can then be used to interact with LaunchDarkly's feature flags.

const { initialize } = require('launchdarkly-js-sdk-common');
const client = initialize('YOUR_ENVIRONMENT_KEY', { key: 'user_key' });

Evaluate Feature Flags

Once the client is ready, you can evaluate feature flags using the `variation` method. This method takes the feature flag key and a default value, returning the flag's value for the user.

client.on('ready', () => {
  const showFeature = client.variation('your-feature-flag-key', false);
  console.log('Feature flag value:', showFeature);
});

Track Custom Events

This feature allows you to track custom events in LaunchDarkly. You can send event data that can be used for analytics and experimentation purposes.

client.track('custom-event-key', { customData: 'value' });

Close the Client

This feature allows you to close the LaunchDarkly client, ensuring that all pending events are sent before the application exits.

client.close();

Other packages similar to launchdarkly-js-sdk-common

unleash-client

The unleash-client package is a feature management client for the Unleash feature flagging system. It provides similar functionality to LaunchDarkly, allowing developers to control feature releases and track feature usage. Unlike LaunchDarkly, Unleash is an open-source solution that can be self-hosted.

flagr

Flagr is an open-source feature flagging and A/B testing tool. The flagr-client package allows developers to interact with the Flagr API to evaluate feature flags and track events. Flagr provides a similar feature set to LaunchDarkly but is designed to be self-hosted and customizable.

README

LaunchDarkly Javascript SDK Core Components

LaunchDarkly overview

LaunchDarkly is a feature management platform that serves trillions of feature flags daily to help teams build better software, faster. Get started using LaunchDarkly today!

Overview

This project provides core implementation components for all of the LaunchDarkly client-side SDKs that use JavaScript: the JS (browser) SDK, the React SDK, the client-side Node SDK, and the Electron SDK. Application code should never refer to the launchdarkly-js-sdk-common package directly.

The initialize function in index.js creates the basic client object that all of those SDKs are built upon. The SDK's own initialize function calls this function, providing a "platform" object that defines additional capabilities specific to that SDK, and then optionally decorates the client object with any other public methods or properties it should have. Inasmuch as possible, the SDK code contains only what is necessary to distinguish it from the other JavaScript-based SDKs. For instance, this project contains no browser-specific code; that is all in js-client-sdk.

It also provides TypeScript definitions in index.d.ts which are re-exported or extended by the SDKs, so the Typedoc documentation for the SDKs includes them.

Contributing

We encourage pull requests and other contributions from the community. Check out our contributing guidelines for instructions on how to contribute to this project.

About LaunchDarkly

• LaunchDarkly is a continuous delivery platform that provides feature flags as a service and allows developers to iterate quickly and safely. We allow you to easily flag your features and manage them from the LaunchDarkly dashboard. With LaunchDarkly, you can:
  • Roll out a new feature to a subset of your users (like a group of users who opt-in to a beta tester group), gathering feedback and bug reports from real-world use cases.
  • Gradually roll out a feature to an increasing percentage of users, and track the effect that the feature has on key metrics (for instance, how likely is a user to complete a purchase if they have feature A versus feature B?).
  • Turn off a feature that you realize is causing performance problems in production, without needing to re-deploy, or even restart the application with a changed configuration file.
  • Grant access to certain features based on user attributes, like payment plan (eg: users on the ‘gold’ plan get access to more features than users in the ‘silver’ plan). Disable parts of your application to facilitate maintenance, without taking everything offline.
• LaunchDarkly provides feature flag SDKs for a wide variety of languages and technologies. Read our documentation for a complete list.
• Explore LaunchDarkly
  • launchdarkly.com for more information
  • docs.launchdarkly.com for our documentation and SDK reference guides
  • apidocs.launchdarkly.com for our API documentation
  • blog.launchdarkly.com for the latest product updates

Changelog

[5.2.0] - 2024-05-01

Added:

• Added an optional timeout to the waitForInitialization method. When a timeout is specified the returned promise will be rejected after the timeout elapses if the client has not finished initializing within that time. When no timeout is specified the returned promise will not be resolved or rejected until the initialization either completes or fails.

Changed:

• The track method now validates that the provided metricValue is a number. If a metric value is provided, and it is not a number, then a warning will be logged.

Fixed:

• Fixed the documentation for evaluationReasons for the identify method.