json-merge-patch

What is json-merge-patch?

The json-merge-patch npm package allows you to apply RFC 7396 JSON Merge Patch operations to JSON documents. This is useful for updating JSON objects by merging changes rather than replacing entire objects.

What are json-merge-patch's main functionalities?

Merging JSON Objects

This feature allows you to merge two JSON objects. The `apply` method takes a target object and a patch object, and returns a new object that is the result of applying the patch to the target.

const jsonMergePatch = require('json-merge-patch');

const target = { a: 1, b: 2 };
const patch = { b: 3, c: 4 };
const result = jsonMergePatch.apply(target, patch);
console.log(result); // { a: 1, b: 3, c: 4 }

Removing Properties

This feature allows you to remove properties from a JSON object by setting their values to `null` in the patch object. The `apply` method will remove the property from the target object.

const jsonMergePatch = require('json-merge-patch');

const target = { a: 1, b: 2, c: 3 };
const patch = { b: null };
const result = jsonMergePatch.apply(target, patch);
console.log(result); // { a: 1, c: 3 }

Nested Merging

This feature allows you to merge nested JSON objects. The `apply` method will recursively merge nested objects, updating only the specified properties.

const jsonMergePatch = require('json-merge-patch');

const target = { a: { b: 1, c: 2 } };
const patch = { a: { c: 3, d: 4 } };
const result = jsonMergePatch.apply(target, patch);
console.log(result); // { a: { b: 1, c: 3, d: 4 } }

Other packages similar to json-merge-patch

deepmerge

The deepmerge package allows you to merge JavaScript objects recursively, which is similar to json-merge-patch. However, deepmerge does not follow the RFC 7396 standard and offers more flexibility in merging strategies.

lodash.merge

The lodash.merge function from the lodash library provides deep merging of objects. It is more versatile and widely used compared to json-merge-patch, but it does not specifically implement the JSON Merge Patch standard.

json-patch

The json-patch package implements the JSON Patch (RFC 6902) standard, which is more complex and powerful than JSON Merge Patch. It allows for a wider range of operations, including adding, removing, and replacing elements in JSON documents.

README

JSON Merge Patch

An implementation of the JSON Merge Patch RFC 7396

JSON Merge Patch (RFC 7396) is a standard format that allows you to update a JSON document by sending the changes rather than the whole document. JSON Merge Patch plays well with the HTTP PATCH verb (method) and REST style programming.

Install

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

npm

$ npm install json-merge-patch --save

Usage

Applying patches:

jsonmergepatch.apply(obj: Object, patch: Object) : Object

Applies patch onto source obj.

Example:

var source = {
  "title": "Goodbye!",
  "author" : {
		"givenName" : "John",
		"familyName" : "Doe"
	}
};

var patch = {
	"title": 'Hello!',
	"author": {
		"familyName": null
	}
}

var target = jsonmergepatch.apply(source, patch);

// target = {
// 	"title": "Hello!",
//   "author" : {
// 		"givenName" : "John",
// 	}
// }

Generating patches:

jsonmergepatch.generate(source: Object, target: Object) : Object

Compares source and target object and generates a patch of the changes necessary to convert source into target.

Example:

var source = {
  "title": "Goodbye!",
  "author" : "John Doe"
};

var target = {
	"title": "Hello!",
};

var patch = jsonmergepatch.generate(source, target);

// patch = {
// 	"title": 'Hello!',
// 	"author": null
// }

Merging patches

This function is outside the scope of the RFC, its purpose is to combine/squash successive patches of the same entity into one patch. Use it at your own risks.

Usage with Javascript objects

This library is primarily designed to work with JSON. Nonetheless, it is possible to use Javascript objects if the method toJSON() is implemented, the library will then serialize your object using it.

var patch = jsonmergepatch.generate(
  {
    "title": "Goodbye!"
  },
  {
    toJSON: () {
      return {
        "title": "I am serialized"
      }
    },
  }
);
// patch = {
// 	"title": "I am serialized",
// }

var patch = jsonmergepatch.generate(
  {},
  {
    date: new Date("2020-05-09T00:00:00.000")
  }
);
// patch = {
// 	date: "2020-05-09T00:00:00.000"
// }

Running tests

npm test

License

MIT