Access express app in LoopBack 4 to add middleware

Question

How can I access the express app instance within a LoopBack 4 application to add a middlware such as helmet or compression via app.use()?

Answer 1

Since the previous answer, LoopBack 4 has provided support for Express.js middleware support alongside the existing LoopBack 4 middleware:

• https://loopback.io/doc/en/lb4/Express-middleware.html
• https://loopback.io/doc/en/lb4/Middleware.html

This includes additional features that enable integration with the Context for dependency injection, wrapping the middleware in a factory function for dynamic configuration, and using it as an interceptor.

Answer 2

LoopBack 4 does not have a first-class support for Express middleware yet, please join the discussion in the following GitHub issue:

• https://github.com/strongloop/loopback-next/issues/1293

Our current recommendation is to create a top-level Express application (where you can mount middleware like helmet) and then mount the LoopBack4 application as a sub-component. You can learn more in the following tutorial:

• Creating an Express Application with LoopBack REST API