LaunchDarkly SDK for Node.js

Quick setup

0. Install the Node.js SDK with npm

    npm install ldclient-node --save
   

1. Require the LaunchDarkly client:

    var LaunchDarkly = require('ldclient-node');
   

2. Create a new LDClient with your SDK key:

    var ld_client = LaunchDarkly.init("YOUR SDK KEY")
   

Your first feature flag

1. Create a new feature flag on your dashboard

2. In your application code, use the feature's key to check whether the flag is on for each user:

    ld_client.once('ready', function() {
      ld_client.variation("your.flag.key", {"key" : "[email protected]"}, false, function(err, show_feature) {
        if (show_feature) {
            # application code to show the feature
        } else {
            # the code to run if the feature is off
        }
      });
    });
   

Learn more

Check out our documentation for in-depth instructions on configuring and using LaunchDarkly. You can also head straight to the complete reference guide for this SDK.

Testing

We run integration tests for all our SDKs using a centralized test harness. This approach gives us the ability to test for consistency across SDKs, as well as test networking behavior in a long-running application. These tests cover each method in the SDK, and verify that event sending, flag evaluation, stream reconnection, and other aspects of the SDK all behave correctly.

Contributing

We encourage pull-requests and other contributions from the community. We've also published an SDK contributor's guide that provides a detailed explanation of how our SDKs work.

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
  • Java
  • JavaScript
  • PHP
  • Python
  • Python Twisted
  • Go
  • Node.JS
  • .NET
  • Ruby
  • iOS
  • Android
• Explore LaunchDarkly
  • launchdarkly.com for more information
  • docs.launchdarkly.com for our documentation and SDKs
  • apidocs.launchdarkly.com for our API documentation
  • blog.launchdarkly.com for the latest product updates
  • Feature Flagging Guide for best practices and strategies