Survivor

Survivor is a tiny (808 byte minified & gzipped) utility for finding the original locations of changed text in a diff.

The intended use case is code diffs with the googlediff library but it can be used for any string diffs and any diffing library that generates diff-match-patch-style output.

Installation

Run npm install survivor.

In the browser, add a script tag referencing survivor.min.js. Since survivor uses UMD, this will expose 'survivor' as a global variable.

Usage

var DiffMatchPath = require('googlediff')
  , survivor = require('survivor')
  , dmp = new DiffMatchPatch()
  , diffs = dmp.diff_main('A quick brown fox', 'A fast brown dog', false)
  , lookup = survivor(diffs)

// lookup 'A' (at the beginning of both lines)
lookup({ line: 0, col: 0 }) // returns { line: 0, col: 0 }

// lookup 'f' from 'fast' (absent from the original)
lookup({ line: 0, col: 2 }) // returns null

// lookup 'b' from 'brown' (moved in the new version)
lookup({ line: 0, col: 7 }) // returns { line: 0, col: 8 }

This lets you look up text changes by line and column. Additionally, it's possible to do basic index-only lookups (treating newlines as just another character). This is done by passing an indexOnly flag to survivor.

var indexOnly = true
  , indexLookup = survivor(diffs, indexOnly)

// lookup 'A' (at the beginning of both lines)
indexLookup(0) // returns 0

// lookup 'f' from 'fast' (absent from the original)
indexLookup(2) // returns null

// lookup 'b' from 'brown' (moved in the new version)
indexLookup(7) // returns 8

Tests

To set up the tests from the repo directory, npm install. And to run them, npm test.

License

MIT