Tiny Merge Patch
================


An implementation of the JSON Merge Patch
RFC 7396: a standard format used to
describe modifications to JSON documents.

This library complies with the functional programming style: it does not mutate
the original target, but recycles what it can.

tiny-merge-patch passes all RFC 7396 tests.

Install

Install the current version (and save it as a dependency):

$3

``sh
npm install tiny-merge-patch --save
`

Import

$3

`js
// Fetch apply from the module.
const mergePatch = require('tiny-merge-patch').apply;
`

$3

`js
// apply is also the default export.
import mergePatch from 'https://unpkg.com/tiny-merge-patch/esm/index.js'
`

Usage

`js
// Original document / object.
const doc = {
a: 'b',
c: { d: 'e', f: 'g' },
h: { i: 0 }
};

// JSON merge patch to apply.
const patch = {
a: 'z',
c: { f: null } // null marks deletions.
};

// Apply the patch.
const patchedDoc = mergePatch(doc, patch);

// tiny-merge-patch complies with the RFC specification.
assert.deepEqual(patchedDoc, {
a: 'z',
c: { d: 'e' },
h: { i: 0 },
});

// Additionally, it does not mutate the original document...
assert(patchedDoc !== doc);

// ...nor its content...
assert(patchedDoc.c !== doc.c);

// ...but recycles what it can.
assert(patchedDoc.h === doc.h);
`

Alternatives

- json-merge-patch (from which this library is forked)

- merge-patch

- json8-merge-patch

All are in-place.
To avoid mutations of the original object, one can deep-clone beforehand, but it can be expensive.
At the contrary, tiny-merge-patch does not alter any of its arguments—but
recycles what it can.
Recycling also allows efficient strict identity-based memoization
(used by React's PureComponent for example).

All of the above libraries also embed additional functionalities, such as patch generation from two objects or merge of patches.
tiny-merge-patch only focuses on the IETF standard and on patch applications.

(None of the above libraries are particularly big.
Still, tiny-merge-patch is smaller if you only need to apply patches.
It is also worth mentioning that unlike
JSON patches, there is no way to
implement merge of merge patches that reliably preserves deletion.)

- immutable-merge-patch`

JSON merge patch implementation for Immutable.js.

License

MIT