A collection of utilities to calculate differences between JavaScript objects. Written in TypeScript, zero dependencies and compatible with most recent Node.js and browser environments.

npm install diff-em

Calculates the differences between two supplied JavaScript objects. The first parameter is regarded as the original object, while the second is the new state. diffObject will return an object with added, updated and deleted properties. Added and updated properties will have the value of the new state object, while deleted properties will return undefined for their keys.

Arrays will be regarded as objects with numeric keys in the resulting difference object.

diffObject has three derivates, which provide a more granular diff. addedDiffObject, updatedDiffObject and deletedDiffObject will only return a resulting object with added properties, updated properties and deleted properties respectively.

import { diffObject } from 'diff-em';

diffObject({ a: 1, b: { c: 2, d: 3 } }, { a: 2, b: { d: 3 }, e: 4 });
// result: { a: 2, b: { c: undefined }, e: 4 }

diffObject({ a: ['b', 'c'] }, { a: ['b', 'd', 'e'] });
// result: { a: { 1: 'd', 2: 'e' }}

import { addedDiffObject, updatedDiffObject, deletedDiffObject } from 'diff-em';

addedDiffObject({ a: 1, b: { c: 2 } }, { a: 2, b: { c: 2, d: 3 }, e: 4 });
// result: { b: { d: 3 }, e: 4 }

updatedDiffObject({ a: 1, b: { c: 2, d: 3 } }, { a: 2, b: { d: 3 }, e: 4 });
// result: { a: 2 }

deletedDiffObject({ a: 1, b: { c: 2, d: 3 } }, { a: 2, b: { d: 3 }, e: 4 });
// result: { b: { c: undefined } }

Calculates the differences between two supplied JavaScript objects and returns an array with JSON Patch (RFC 6902) operation objects.

Like diffObject, arrays will be regarded as objects with numeric keys in the resulting paths.

import { diffPatch } from 'diff-em';

diffPatch({ a: 1, b: { c: 2, d: 3 } }, { a: 2, b: { d: 3 }, e: 4 });
// result:
// [
//  {"op": "replace", "path": "/a", "value": 2},
//  {"op": "remove", "path": "/b/c"},
//  {"op": "add", "path": "/e", "value": 4}
// ]

diffPatch({ a: ['b', 'c'] }, { a: ['b', 'd', 'e'] });
// result:
// [
//  {"op": "replace", "path": "/a/1", "value": "d"},
//  {"op": "add", "path": "/a/2", "value": "e"}
// ]

Calculates the differences between two supplied JavaScript objects and returns an array with strings in JSONPath format. The entries of the array may indicate an added, updated or deleted property between the two objects. For a more granular diff, use addedDiffPath, updatedDiffPath and deletedDiffPath. These will only return paths for added properties, updated properties and deleted properties respectively.

Like diffObject, arrays will be regarded as objects with numeric keys in the resulting paths.

import { diffPath } from 'diff-em';

diffPath({ a: 1, b: { c: 2, d: 3 } }, { a: 2, b: { d: 3 }, e: 4 });
// result: ['$.a', '$.b.c', '$.e']

diffPath({ a: ['b', 'c'] }, { a: ['b', 'd', 'e'] });
// result: ['$.a.1', '$.a.2']

import { addedDiffPath, updatedDiffPath, deletedDiffPath } from 'diff-em';

addedDiffPath({ a: 1, b: { c: 2 } }, { a: 2, b: { c: 2, d: 3 }, e: 4 });
// result: ['$.b.d', '$.e']

updatedDiffPath({ a: 1, b: { c: 2, d: 3 } }, { a: 2, b: { d: 3 }, e: 4 });
// result: ['$.a']

deletedDiffPath({ a: 1, b: { c: 2, d: 3 } }, { a: 2, b: { d: 3 }, e: 4 });
// result: ['$.b.c']

Diff 'em is released under the MIT license.

• Thanks to Matt Phillips for the original code and idea this repository was based on.