Find the differences between two arrays and their positions

Usage no npm install needed!

<script type="module">
  import arrayDifferences from '';



npm version

Find the differences between two arrays and their positions.


npm install array-differences --save


yarn add array-differences


import arrayDifferences from 'array-differences'

const input = [0, 1, 1, 4, 1, 1]
const output = [111, 1, 112, 1, 4, 1]
const diff = arrayDifferences(input, output)

--> [['modified', 0, 111], ['inserted', 2, 112], ['deleted', 5]]

Using a custom comparison function:

const diff = arrayDifferences(
  [{ name: 'John' }, { name: 'Marie' }],
  [{ name: 'John' }, { name: 'Marie' }, { name: 'Chloe' }],
  (a, b) => ===

--> [['inserted', 2, { name: 'Chloe' }]]

You can recontruct the second array by iterating over the differences on the first array or using the utility:

import { reconstructArray } from 'array-differences'

const reconstructed = reconstructArray(input, diff) // builds the output

// You can reconstruct in place:
reconstructArray(input, diff, true) // modifies input to recreate output from diff

Undefined values

The algorythm does not support arrays containing undefined values. Please replace your undefined values with a placeholder before applying it.

Performance on large arrays

Entry one is length n,

Entry two is length m,

Perfomance is n * n * m.

Therefore, it works best on smaller first arrays or if growing an array. Performance is best when differences indexes are close to one another in the array.