why does NPM install extra modules?

I am new to web development, currently learning Node.js and Express is the first web framework i am diving into, since that's the stack the online course i am following work with (and i am quite happy with it).
While trying to to npm install Express to the directory i am working in, i have noticed that not only express module was install but also a bunch of other modules:

So, my questions is: What's the need for all those extra modules? and are they necessary for express to function well?

and Thanks in advance

Comments

[Connor Phee]

Hamza,

The reason for all of those extra modules is that Express depends on those. If you check out Express on NPM: npmjs.com/package/express

you can see the dependency list on the right side of the page matches those extra packages in your node_modules.

This is common for larger packages since it is much easier to find an existing package that solves a problem, rather than having to write it from scratch, similar to how you're using Express to simplify/abstract some things.

Also worth noting: Not only are the dependencies of Express installed, but also the dependencies of the dependencies, and that goes for every level until every needed package exists.

Hope this helps!

[Hamza]

I couldn't find a simpler answer, you really explained everything I wanted to know and some more.
Thank you so much Connor

[Theofanis Despoudis]

There is a well known joke about node modules...

[Arden de Raaij]

Even though it's so true, I'm still happy with it. I remember Ruby Dependency hell and it wasn't pretty..

[Leah]

I still think it could be better and people should think twice before including new dependencies

Especially when there's nested dependencies

[Hamza]

Haha, but i suppose it's better that way, I'll get to look up a the dependencies of the module I'm installing and so I'll know that module better than if it included every thing itself.

[Joshua Johnson]

Node installs all modules required by any modules you depend on. In the case of express. It has a number of modules that have to be pulled in to properly run.

[Hamza]

Yes, so it seems! Cause I was wondering what are all these modules, am I doing something wrong, turns out npm installed what it's supposed to.
And that's why I love programming I learn something new every time I ask a question.
Thank you Joshua