Module @openfeature/core - v1.10.0

Shared js components (server and web)

OpenFeature is an open specification that provides a vendor-agnostic, community-driven API for feature flagging that works with your favorite feature flag management tool.

🔩 Shared JS components

[!IMPORTANT] If you're developing a provider or hook, you probably do not want to use this package!

This package comprises the common types and interfaces of the OpenFeature server and web SDKs. If you are developing a provider or a hook, you should instead utilize the server or web SDKs. This package is useful if you need to reference the underlying types common to all the JS SDKs or if you're creating a utility that can be used for both server and web implementations. Be sure to add this module as either a devDependency (if only build time assets such as types are required) or as a peerDependency with a permissive version expression.

Type-Safe Flag Keys

This package provides TypeScript types that allow consumers to enforce type safety for flag keys through module augmentation. By default, all flag key types (BooleanFlagKey, StringFlagKey, NumberFlagKey, ObjectFlagKey) are defined as string, but consumers can override them to restrict flag keys to specific values.

To provide type-safe flag keys, create a TypeScript declaration file (e.g., types.d.ts) in your project and use module augmentation:

declare module '@openfeature/core' {
  export type BooleanFlagKey = 'enable-feature-a' | 'show-beta-ui' | 'allow-experimental';
  export type StringFlagKey = 'theme-color' | 'welcome-message';
  export type NumberFlagKey = 'max-retries' | 'timeout-seconds';
  export type ObjectFlagKey = 'user-preferences' | 'feature-config';
}
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Overriding these types will allow for all methods that fetch flag values to enforce that only the specified keys can be used in TypeScript, providing better type safety and reducing the likelihood of typos or incorrect flag key usage, while also providing type-ahead suggestions in IDEs.

API Reference

See here for the complete API documentation.