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An implementation of the JSON Merge PatchRFC 7396: a standard format used todescribe modifications to JSON documents.

This library complies with the functional programming style: it does not mutatethe original target, but recycles what it can. It is particularly appropriate to update a state used byReact, allowing selective re-rendering of the UI.

tiny-merge-patch passes allRFC 7396 tests.

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

npm install tiny-merge-patch --save

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

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

// Original document / object.constdoc={a:'b',c:{d:'e',f:'g'},h:{i:0}};// JSON merge patch to apply.constpatch={a:'z',c:{f:null}// null marks deletions.};// Apply the patch.constpatchedDoc=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);

• 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—butrecycles what it can.Recycling also allows efficient strict identity-based memoization(used byReact'sPureComponent 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 unlikeJSON patches, there is no way toimplement merge of merge patches that reliably preserves deletion.)

• immutable-merge-patch: JSON merge patch implementation forImmutable.js.

MIT