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Diff Background

Diff Background is a library to compare two values an get an object representing the differences between them. This object represents one of 3 possible changes: Create, Update, or Delete, and also has a path to know where did the change happen inside the given values.


I was using deep-diff for a while in my test library, but that was making my library way heavier than it needed to be, with features I wasn’t fully using and a syntax I didn’t fully liked (the identifiers for the type of changes are single letters instead of words).

Because of that, I decided to try to create my own diffing library, and this is the result of that effort.


I built this library using TypeScript, with configurations from my shared configs. I made it ESM only as soon as Node started supporting ESM modules, and I made it tree-shakeable by using named exports.

The idea was to create a leaner alternative to deep-diff, so instead of taking a look at their code, I just took their output as a reference, and implemented the diffing code myself.

To make it fast, I used generators instead of plain arrays. The final result ended up being something I really like: A faster, simpler and smaller alternative to deep-diff, making my test also faster, simpler and smaller in the process.


As I pointed out a few times in previous sections, I’m using this library in my test library, and I’m pretty happy with it. So far I haven’t used it elsewhere, but it might prove useful in the future.