Environment Variable Provider

The environment variable provider is a great way to start using OpenFeature. It doesn't require any infrastructure to setup or manage, and provides a simple way to gain experience with the core concepts of feature flagging. However, it doesn't support features such as dynamic updates at run-time or contextual flag evaluation. That's where feature flags become extremely powerful! Thankfully, the OpenFeature SDK supports basic providers such at this one, while making it simple to switch to a more powerful system when the time is right.

Installation

$ npm install @openfeature/env-var-provider

Required peer dependencies

$ npm install @openfeature/server-sdk

Usage

The environment variable provider uses environment variables to determine the value of a feature flag. It supports booleans, strings, numbers and objects by attempting to interpret the value of an environment variable to the requested type. The default value will be returned if the environment variable doesn't exist or the value can't be cast to the desired type.

1// Register the environment variable provider globally
2OpenFeature.setProvider(new EnvVarProvider());

Available options

Option name	Type	Default
disableConstantCase	boolean	false

Examples

Boolean example

1# Start a hypothetical application with the ENABLE_NEW_FEATURE environment variable
2ENABLE_NEW_FEATURE=true node my-app.js

1const client = OpenFeature.getClient();
2client.getBooleanValue('enable-new-feature', false);

Number example

1# Start a hypothetical application with the DIFFICULTY_MULTIPLIER environment variable
2DIFFICULTY_MULTIPLIER=5 node my-app.js

1const client = OpenFeature.getClient();
2client.getNumberValue('difficulty-multiplier', 0);

String example

1# Start a hypothetical application with the WELCOME_MESSAGE environment variable
2WELCOME_MESSAGE=yo node my-app.js

1const client = OpenFeature.getClient();
2client.getStringValue('welcome-message', 'hi');

Object example

1# Start a hypothetical application with the PREFERRED_SDK environment variable
2PREFERRED_SDK='{"name": "openfeature"}' node my-app.js

1const client = OpenFeature.getClient();
2client.getObjectValue('preferred-sdk', { name: 'OpenFeature' });

Development

Building

Run nx package providers-env-var to build the library.

Running unit tests

Run nx test providers-env-var to execute the unit tests via Jest.