@sanity/diff-match-patch

A TypeScript fork of the JavaScript version of google/diff-match-patch, that includes a few long-standing pull requests, fixing certain bugs and with an API more familiar to the JavaScript ecosystem.

Installing

npm install --save @sanity/diff-match-patch

What is diff-match-patch?

The Diff Match and Patch libraries offer robust algorithms to perform the operations required for synchronizing plain text.

Diff:
- Compare two blocks of plain text and efficiently return a list of differences.
- Diff Demo
Match:
- Given a search string, find its best fuzzy match in a block of plain text. Weighted for both accuracy and location.
- Match Demo
Patch:
- Apply a list of patches onto plain text. Use best-effort to apply patch even when the underlying text doesn't match.
- Patch Demo

Originally built in 2006 to power Google Docs, this library is now available in C++, C#, Dart, Java, JavaScript, Lua, Objective C, and Python.

API

Creating and applying patches

import {makePatches, applyPatches, stringifyPatches, parsePatches} from '@sanity/diff-match-patch'

// Make array of diffs in internal array format, eg tuples of `[DiffType, string]`
const patches = makePatches('from this', 'to this')

// Make unidiff-formatted (string) patch
const patch = stringifyPatches(patches)

// Apply the patch (array representation)
const [newValue] = applyPatches(patches, 'from this')

// Apply the patch (unidiff-formatted)
const [alsoNewValue] = applyPatches(parsePatch(patch), 'from this')

Creating diffs

import {makeDiff} from '@sanity/diff-match-patch'

// Make an array of diff tuples, eg `[DiffType, string]`
const diff = makeDiff('from this', 'to this')

Matching text

import {match} from '@sanity/diff-match-patch'

// Find position in text for the given pattern, at the approximate location given
const position = match('some text to match against', 'match', 9)

Applying patches

import {applyPatches} from '@sanity/diff-match-patch'

const [newValue, results] = applyPatches(patch, 'source text')
const matches = results.filter((matched) => matched === true).length
const misses = results.length - matches
console.log('Patch applied with %d matches and %d misses', matches, misses)
console.log('New value: %s', newValue)

Migrating from `diff-match-patch`

The original library that this is a fork of has a different API, meaning this fork is not a drop-in replacement. Here's a breakdown of the most common operations and their API differences:

Creating diffs

-import {diff_match_patch as DiffMatchPatch} from 'diff-match-patch'
-const dmp = new DiffMatchPatch()
-const diffs = dmp.diff_main('from this', 'to this')
-dmp.diff_cleanupSemantic(diffs)
+import {makeDiff, cleanupSemantic} from '@sanity/diff-match-patch'
+const diffs = cleanupSemantic(makeDiff('from this', 'to this'))

Make patches

-import {diff_match_patch as DiffMatchPatch} from 'diff-match-patch'
-const dmp = new DiffMatchPatch()
-const rawPatch = dmp.patch_make('from this', 'to this')
-const patch = rawPatch.map(p => p.toString()).join('')
+import {makePatches, stringifyPatches} from '@sanity/diff-match-patch'
+const patch = stringifyPatches(makePatches('from this', 'to this'))

Apply patches

-import {diff_match_patch as DiffMatchPatch} from 'diff-match-patch'
-const dmp = new DiffMatchPatch()
-const patch = dmp.patch_fromText('some-text-patch')
-const [newValue] = dmp.patch_apply(patch, 'source text')
+import {applyPatches, parsePatch} from '@sanity/diff-match-patch'
+const [newValue] = applyPatches(parsePatch('some-text-patch'), 'source text')

Algorithms

This library implements Myer's diff algorithm which is generally considered to be the best general-purpose diff. A layer of pre-diff speedups and post-diff cleanups surround the diff algorithm, improving both performance and output quality.

This library also implements a Bitap matching algorithm at the heart of a flexible matching and patching strategy.

Significant changes in fork

This fork has a few modifications to the original:

Written in TypeScript, and shipped with CommonJS and ES module builds
API has changed - individual methods are exposed as importable functions instead of being attached to a DiffMatchPatch prototype. Enables better tree-shaking.
Includes a fix for surrogate pair handling
Includes a fix for indicies calculated using UCS-2 instead of UTF-8
Uses modern tooling for code compilation and testing