fast-diff

What is fast-diff?

The fast-diff npm package is a JavaScript library that provides a fast and efficient way to compute the difference between two strings. It is commonly used to implement text comparison features, such as in diff tools or for highlighting changes in text documents.

What are fast-diff's main functionalities?

Compute Difference

This feature allows you to compute the difference between two strings. The function returns an array of tuples, where each tuple represents a part of the diff and its type (addition, deletion, or no change).

const diff = require('fast-diff');
const text1 = 'hello world';
const text2 = 'hello new world';
const changes = diff(text1, text2);
console.log(changes);

Customizable Diff Function

fast-diff allows you to customize the diff function by passing an optional cursor position to optimize the diff computation around that cursor location. This is useful for real-time editing applications.

const diff = require('fast-diff');
const text1 = 'goodbye world';
const text2 = 'goodbye cruel world';
const changes = diff(text1, text2, diff.EQUAL);
console.log(changes);

Other packages similar to fast-diff

jsdiff

jsdiff (also known as 'diff') is a library that provides a set of functions for computing text differences. It offers more features than fast-diff, such as character, word, line, and sentence diffs, as well as applying patches. However, it might be slower for certain operations compared to fast-diff.

google-diff-match-patch

This library offers a robust set of algorithms for performing text diffs and patches. It is designed to handle larger texts and provide more complex functionalities like patching and match functionalities. It is more feature-rich but also more complex and potentially slower than fast-diff.

README

Fast Diff

This is a simplified import of the excellent diff-match-patch library by Neil Fraser into the Node.js environment. The match and patch parts are removed, as well as all the extra diff options. What remains is incredibly fast diffing between two strings.

The diff function is an implementation of "An O(ND) Difference Algorithm and its Variations" (Myers, 1986) with the suggested divide and conquer strategy along with several optimizations Neil added.

var diff = require('fast-diff');

var good = 'Good dog';
var bad = 'Bad dog';

var result = diff(good, bad);
// [[-1, "Goo"], [1, "Ba"], [0, "d dog"]]

// Respect suggested edit location (cursor position), added in v1.1
diff('aaa', 'aaaa', 1)
// [[0, "a"], [1, "a"], [0, "aa"]]

// For convenience
diff.INSERT === 1;
diff.EQUAL === 0;
diff.DELETE === -1;