jest-diff

What is jest-diff?

The jest-diff npm package is a utility primarily used to show differences between two values, typically used in testing environments to assert the equality of objects, arrays, or other data structures. It is part of the Jest testing framework but can be used independently for its diffing capabilities.

What are jest-diff's main functionalities?

Diffing two values

This feature allows you to compare two JavaScript objects and outputs a string that visually represents the differences between them. It is useful for debugging and in test assertions to see what exactly differs when a test fails.

const diff = require('jest-diff');
const a = { a: { b: { c: 5 } } };
const b = { a: { b: { c: 6 } } };
console.log(diff(a, b));

Customizing diff output

This feature allows customization of the diff output by passing options. You can specify annotations for the compared values, which helps in making the output more understandable and tailored to specific needs.

const diff = require('jest-diff');
const options = { aAnnotation: 'First', bAnnotation: 'Second' };
const a = [1, 2, 3];
const b = [2, 1, 3];
console.log(diff(a, b, options));

Other packages similar to jest-diff

deep-diff

Deep-diff is a library that provides a detailed analysis of differences between any two JavaScript objects. It is more granular than jest-diff as it provides more detailed information about the type of change (edit, delete, add), which can be useful for more complex diffing needs.

diff

The 'diff' package is another popular choice for computing differences between texts. It is not limited to JavaScript objects and can handle strings effectively, making it suitable for applications like text editors or any scenario where text comparison is needed. Unlike jest-diff, it does not provide a structured view for object differences.