When do you use a JavaScript library instead of writing your own code?

In my article on myths about vanilla JS, I mentioned that vanilla JS doesn’t mean you always write everything from scratch yourself…

I use helper functions and small libraries all the time. A lot of very talented people have done a lot of great work to make the web faster, safer, and easier to build. Stand on their shoulders!

One common question I get whenever I say that is…

So… when do you choose to use a library? And which libraries do you use?

I tend to reach for libraries for things that are complicated or involve a lot of moving parts.

For me, that often means “media and animation stuff” like interactive image galleries. I use PhotoSwipe for that. It also means security stuff like data sanitization. I use DOMPurify for that. And it means complicated math stuff like currencies. I use Dinero.js for that.

And if I wrote my own code, but I think it’s something I might reuse on other projects, I’ll often make it into a library that can be easily customized through options and settings.

I maintain a list of libraries that I use and enjoy over at the Vanilla JS Toolkit.