generic-diff

Diff arrays or array-like objects, such as strings. Based on "An O(ND) Difference Algorithm and its Variations" (Myers, 1986).

diff( a, b [, eql] )

Diffs the array-like objects a and b, returning a summary of edits required to turn a into b. Defaults to using strict equality (===) to compare items in a and b. A comparison function, eql, can optionally be used for more nuanced comparisons; the signature of this function is (item from a, item from b) => Boolean.

The “summary of changes” is an array of objects with three properties: items, an array of one or more items from a or b, and boolean properties added and removed, indicating whether the item(s) should be added or removed from a, respectively. For example, if we’re diffing the strings abc and abd, the summary of changes would look like:

[{
  items: ['a', 'b'],
  added: false,
  removed: false
}, {
  items: ['c'],
  added: false,
  removed: true
}, {
  items: ['d'],
  added: true,
  removed: false
}]

Example

Diff two strings, creating an HTML representation of their differences:

var diff = require('generic-diff')

var changes = diff('falafel', 'fallacy')
changes = changes.map(function (edit) {
  if (edit.added) {
    return '<ins>' + edit.items.join('') + '</ins>'
  } else if (edit.removed) {
    return '<del>' + edit.items.join('') + '</del>'
  } else {
    return edit.items.join('')
  }
}).join('')

console.log(changes)
// 'fal<del>afe</del>l<ins>acy</ins>'

For a slightly more involved example, this gist demonstrates how to diff two files and produce an output similar to the UNIX diff command.

LICENSE

MIT