Your Product Manager has added a note that we should first integrate with the Stripe payment gateway but it’s likely the business will change to another payment gateway in a few months (for the record, I ❤️ Stripe, this is just a hypothetical 🙂). Your next task in the backlog is to integrate with a payment gateway.

It’s been running for a few months, gaining users, and now the business wants to enable customers to upgrade to a premium account.

You’re building a REST API that’s written with Node/Express and TypeScript.

We’ll use a realistic, but hypothetical scenario to see the benefits of dependency injection: It also has the added benefit of making your code easier to test. Why use it?ĭependency injection decouples your code which makes your application more adaptable to changing requirements. Instead, they should receive their dependencies as arguments and let other code deal with setting up the dependency.ĭependency injection is the group of techniques used to enable a class or function to specify what dependencies they need without needing to worry about the details on how to get or create each dependency. Very roughly, the Dependency inversion principle states that functions or classes shouldn’t be concerned with building / instantiating their dependencies. What is dependency injection?ĭependency injection is a solution to implement Inversion of Control, which is one of the SOLID principles (D: Dependency inversion). Let’s find out what exactly is dependency injection, what are its benefits and how to build a simple but effective dependency injection solution in Express.js with the help of TypeScript. Unfortunately, that’s not the case for most Node.js web frameworks, including Express.js. Web frameworks like Spring and ASP.NET Core have dependency injection solutions built in.

Express typescript