A lightweight A/B Testing and Feature Flag JavaScript library focused on performance ⚡️
Tesfy provides a simple but complete solution to develop A/B Tests and Feature Flags on both server and client side without relying in any storage layer. The main features of this library are: - Lightweight and focused on performance - Experiments - Feature Flags - Audience definition using [jsonLogic](http://jsonlogic.com/) - Traffic Allocation - Sticky Bucketing ## Usage ### Installation ```sh npm install tesfy --save ``` ### Initialization Import and instantiate it with a datafile. A datafile is a `json` that defines the experiments and features avaliable. Ideally this file should be hosted somewhere outside your application (for example in [S3](https://aws.amazon.com/s3/)), so it could be fetched during boostrap or every certain time. This will allow you to make changes to the file without deploying the application. ```ts import * as Tesfy from 'tesfy'; const datafile = { experiments: { 'experiment-1': { id: 'experiment-1', percentage: 90, variations: [{ id: '0', percentage: 50 }, { id: '1', percentage: 50 }] }, 'experiment-2': { id: 'experiment-2', percentage: 100, variations: [{ id: '0', percentage: 100 }], audience: { '==' : [{ var : 'countryCode' }, 'us'] } } }, features: { 'feature-1': { id: 'feature-1', percentage: 50 } } }; const tesfy = new Tesfy.Engine({ datafile }); ``` ### Experiments Check which variation of an experiment is assigned to a user. ```ts const userId = '676380e0-7793-44d6-9189-eb5868e17a86'; const experimentId = 'experiment-1'; tesfy.getVariationId(experimentId, userId); // '1' ``` ### Feature Flags Check if a feature is enabled for a user. ```ts const userId = '676380e0-7793-44d6-9189-eb5868e17a86'; const featureId = 'feature-1'; tesfy.isFeatureEnabled(featureId, userId); // true ``` ### Audiences Use attributes to target an specific audience. ```ts const userId = '676380e0-7793-44d6-9189-eb5868e17a86'; const experimentId = 'experiment-2'; tesfy.getVariationId(experimentId, userId, { countryCode: 've' }); // null tesfy.getVariationId(experimentId, userId, { countryCode: 'us' }); // '0' ``` ### Sticky Bucketing Optionally add a storage layer when instantiating tesfy. This layer could be whatever you want (memory cache, [localStorage](https://developer.mozilla.org/en-US/docs/Web/API/Window/localStorage) among others). This way even allocation or attributes change users will stick with same variation. ```ts const tesfy = new Tesfy.Engine({ datafile, storage: { get: (experimentId: string) => { return storage.get(experimentId); }, store: (experimentId: string, variationId: string) => { return storage.save(experimentId, variationId); } } }); const userId = '676380e0-7793-44d6-9189-eb5868e17a86'; const experimentId = 'experiment-2'; tesfy.getVariationId(experimentId, userId, { countryCode: 'us' }); // '0' tesfy.getVariationId(experimentId, userId, { countryCode: 've' }); // '0' ``` ## Integrations Tesfy could be integrated with several JavaScript frameworks or libraries to provide a better API to use alongside those. - [react-tesfy](https://github.com/andresz1/react-tesfy) ## Feedback Pull requests, feature ideas and bug reports are very welcome. We highly appreciate any feedback.
