fflip integration for the express.js web framework
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fflip-express is an Express.js integration for the fflip feature-flagging library.

npm install fflip-express --save


var FFlipExpressIntegration = require('fflip-express');

// The first `fflip` argument is the fflip module used in your application
// The second `options` argument is optional, and lets you configure your integration
var fflipExpress = new FFlipExpressIntegration(fflip, options);

Available configuration options include:

  • cookieName: The name of the cookie where a users manual feature flags will be saved. (Defaults to 'fflip')
  • cookieOptions: Set additional options for the fflip cookie, such as expires & maxAge. (No default)
  • manualRoutePath: The URL path for the manual feature flipping endpoint. Must include both :name and :action route params. (Defaults to '/fflip/:name/:action')


This integration provides two different ways to connect fflip into your express application; both of them require that you have req.cookies available from cookieParser:




req.fflip: A special fflip request object is attached to the request object, and includes the following functionality:

req.fflip = {
  setForUser(user): Given a user, attaches the features object to the request (at req.fflip.features). Make sure you do this before calling has()!
  has(featureName): Given a feature name, returns the feature boolean, undefined if feature doesn't exist. Throws an error if setForUser() hasn't been called

Use fflip in your templates: Once setForUser() has been called, fflip will include a Features template variable that contains your user's enabled features. Here is an example of how to use it with Handlebars: {{#if Features.closedBeta}} Welcome to the Beta! {{/if}}

Use fflip on the client: Once setForUser() has been called, fflip will also include a FeaturesJSON template variable that is the JSON string of your user's enabled features. To deliver this down to the client, just make sure your template something like this: <script>var Features = {{ FeaturesJSON }}; </script>.


// Feel free to use any route you'd like, as long as `name` & `action` exist as route parameters.
app.get('/custom_path/:name/:action', fflipExpress.manualRoute);

A route for manually flipping on/off features: If you have cookies enabled, you can visit this route to manually override a feature to always return true/false for your own session. Just replace ':name' with the Feature name and ':action' with 1 to enable, 0 to disable, or -1 to reset (remove the cookie override). This override is stored in the user's cookie under the name fflip, which is then read by fflip.expressMiddleware() and req.fflip automatically.


Sets up the express middleware and route automatically. Equivilent to running:

app.get(fflipExpress.options.manualRoutePath, fflipExpress.manualRoute);