How fn(args, deps) supports SOLID-style design in TypeScript

A lot of developers learn the SOLID principles through class-heavy examples.

That is probably why the conversation so often gets stuck there.

People start to associate SOLID with inheritance hierarchies, interface forests, service classes, and object-oriented ceremony.

But the useful part is not the ceremony.

It is the design pressure.

One of the simplest ways to apply that pressure in plain TypeScript is this shape:

fn(args, deps)

Where args is the input for this call and deps is the set of collaborators the function needs. You can read that as: data in, capabilities in.

fn(args, deps) is not a replacement for SOLID. It is a simple function shape that makes several SOLID ideas easier to apply without forcing you into class-heavy design.