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https://github.com/Starcounter-Jack/JSON-Patch

Lean and mean Javascript implementation of the JSON-Patch standard (RFC 6902). Update JSON documents using delta patches.
https://github.com/Starcounter-Jack/JSON-Patch

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Lean and mean Javascript implementation of the JSON-Patch standard (RFC 6902). Update JSON documents using delta patches.

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JSON-Patch

===============



> A leaner and meaner implementation of JSON-Patch. Small footprint. High performance.



[![Build Status](https://travis-ci.org/Starcounter-Jack/JSON-Patch.svg?branch=master)](https://travis-ci.org/Starcounter-Jack/JSON-Patch)



With JSON-Patch, you can:

- **apply** patches (arrays) and single operations on JS object

- **validate** a sequence of patches

- **observe** for changes and **generate** patches when a change is detected

- **compare** two objects to obtain the difference



Tested in Firefox, Chrome, Edge, Safari, IE11, Deno and Node.js



## Why you should use JSON-Patch



JSON-Patch [(RFC6902)](http://tools.ietf.org/html/rfc6902) is a standard format that

allows you to update a JSON document by sending the changes rather than the whole document.

JSON Patch plays well with the HTTP PATCH verb (method) and REST style programming.



Mark Nottingham has a [nice blog]( http://www.mnot.net/blog/2012/09/05/patch) about it.



## Install



[Download as ZIP](https://github.com/Starcounter-Jack/JSON-Patch/archive/master.zip) or install the current version using a package manager (and save it as a dependency):



```sh

# NPM

npm install fast-json-patch --save

```



## Adding to your project



### In a web browser



Load the bundled distribution script:



```html



```



In [browsers that support ECMAScript modules](https://caniuse.com/#feat=es6-module), the below code uses this library as a module:



```html



  import * as jsonpatch from 'fast-json-patch/index.mjs';

  import { applyOperation } from 'fast-json-patch/index.mjs';



```



### In Node.js



In Node 12+ with `--experimental-modules` flag, the below code uses this library as an ECMAScript module:



```js

import * as jsonpatch from 'fast-json-patch/index.mjs';

import { applyOperation } from 'fast-json-patch/index.mjs';

```



In Webpack (and most surely other bundlers based on Babel), the below code uses this library as an ECMAScript module:



```js

import * as jsonpatch from 'fast-json-patch';

import { applyOperation } from 'fast-json-patch';

```



In standard Node, the below code uses this library as a CommonJS module:



```js

const { applyOperation } = require('fast-json-patch');

const applyOperation = require('fast-json-patch').applyOperation;

```



## Directories



Directories used in this package:



- `dist/` - contains ES5 files for a Web browser

- `commonjs/` - contains CommonJS module and typings

- `module/` - contains ECMAScript module and typings

- `src/` - contains TypeScript source files



## API



#### `function applyPatch(document: T, patch: Operation[], validateOperation?: boolean | Validator, mutateDocument: boolean = true, banPrototypeModifications: boolean = true): PatchResult`



Applies `patch` array on `obj`.



- `document` The document to patch

- `patch` a JSON-Patch array of operations to apply

- `validateOperation` Boolean for whether to validate each operation with our default validator, or to pass a validator callback

- `mutateDocument` Whether to mutate the original document or clone it before applying

- `banPrototypeModifications`  Whether to ban modifications to `__proto__`, defaults to `true`.



An invalid patch results in throwing an error (see `jsonpatch.validate` for more information about the error object).



It modifies the `document` object and `patch` - it gets the values by reference.

If you would like to avoid touching your `patch` array values, clone them: `jsonpatch.applyPatch(document, jsonpatch.deepClone(patch))`.



Returns an array of [`OperationResult`](#operationresult-type) objects - one item for each item in `patches`, each item is an object `{newDocument: any, test?: boolean, removed?: any}`.



* `test` - boolean result of the test

* `remove`, `replace` and `move` - original object that has been removed

* `add` (only when adding to an array) - index at which item has been inserted (useful when using `-` alias)



- ** Note: It throws `TEST_OPERATION_FAILED` error if `test` operation fails. **

- ** Note II: the returned array has `newDocument` property that you can use as the final state of the patched document **.

- ** Note III: By default, when `banPrototypeModifications` is `true`, this method throws a `TypeError` when you attempt to modify an object's prototype.



- See [Validation notes](#validation-notes).



Example:



```js

var document = { firstName: "Albert", contactDetails: { phoneNumbers: [] } };

var patch = [

  { op: "replace", path: "/firstName", value: "Joachim" },

  { op: "add", path: "/lastName", value: "Wester" },

  { op: "add", path: "/contactDetails/phoneNumbers/0", value: { number: "555-123" }  }

];

document = jsonpatch.applyPatch(document, patch).newDocument;

// document == { firstName: "Joachim", lastName: "Wester", contactDetails: { phoneNumbers: [{number:"555-123"}] } };

```



#### `function applyOperation(document: T, operation: Operation, validateOperation: boolean | Validator = false, mutateDocument: boolean = true, banPrototypeModifications: boolean = true, index: number = 0): OperationResult`



Applies single operation object `operation` on `document`.



- `document` The document to patch

- `operation` The operation to apply

- `validateOperation` Whether to validate the operation, or to pass a validator callback

- `mutateDocument` Whether to mutate the original document or clone it before applying

- `banPrototypeModifications` Whether to ban modifications to `__proto__`, defaults to `true`.

- `index` The index of the operation in your patch array. Useful for better error reporting when that operation fails to apply.



It modifies the `document` object and `operation` - it gets the values by reference.

If you would like to avoid touching your values, clone them: `jsonpatch.applyOperation(document, jsonpatch.deepClone(operation))`.



Returns an [`OperationResult`](#operationresult-type) object `{newDocument: any, test?: boolean, removed?: any}`.



- ** Note: It throws `TEST_OPERATION_FAILED` error if `test` operation fails. **

- ** Note II: By default, when `banPrototypeModifications` is `true`, this method throws a `TypeError` when you attempt to modify an object's prototype.



- See [Validation notes](#validation-notes).



Example:



```js

var document = { firstName: "Albert", contactDetails: { phoneNumbers: [] } };

var operation = { op: "replace", path: "/firstName", value: "Joachim" };

document = jsonpatch.applyOperation(document, operation).newDocument;

// document == { firstName: "Joachim", contactDetails: { phoneNumbers: [] }}

```



#### `jsonpatch.applyReducer(document: T, operation: Operation, index: number): T`



**Ideal for `patch.reduce(jsonpatch.applyReducer, document)`**.



Applies single operation object `operation` on `document`.



Returns the a modified document.



Note: It throws `TEST_OPERATION_FAILED` error if `test` operation fails.



Example:



```js

var document = { firstName: "Albert", contactDetails: { phoneNumbers: [ ] } };

var patch = [

  { op:"replace", path: "/firstName", value: "Joachim" },

  { op:"add", path: "/lastName", value: "Wester" },

  { op:"add", path: "/contactDetails/phoneNumbers/0", value: { number: "555-123" } }

];

var updatedDocument = patch.reduce(applyReducer, document);

// updatedDocument == { firstName:"Joachim", lastName:"Wester", contactDetails:{ phoneNumbers[ {number:"555-123"} ] } };

```



#### `jsonpatch.deepClone(value: any): any`



Returns deeply cloned value.



#### `jsonpatch.escapePathComponent(path: string): string`



Returns the escaped path.



#### `jsonpatch.unescapePathComponent(path: string): string`



Returns the unescaped path.



#### `jsonpatch.getValueByPointer(document: object, pointer: string)`



Retrieves a value from a JSON document by a JSON pointer.



Returns the value.



#### `jsonpatch.observe(document: any, callback?: Function): Observer`



Sets up an deep observer on `document` that listens for changes in object tree. When changes are detected, the optional

callback is called with the generated patches array as the parameter.



Returns `observer`.



#### `jsonpatch.generate(document: any, observer: Observer, invertible = false): Operation[]`



If there are pending changes in `obj`, returns them synchronously. If a `callback` was defined in `observe`

method, it will be triggered synchronously as well. If `invertible` is true, then each change will be preceded by a test operation of the value before the change.



If there are no pending changes in `obj`, returns an empty array (length 0).



Example:



```js

var document = { firstName: "Joachim", lastName: "Wester", contactDetails: { phoneNumbers: [ { number:"555-123" }] } };

var observer = jsonpatch.observe(document);

document.firstName = "Albert";

document.contactDetails.phoneNumbers[0].number = "123";

document.contactDetails.phoneNumbers.push({ number:"456" });

var patch = jsonpatch.generate(observer);

// patch  == [

//   { op: "replace", path: "/firstName", value: "Albert"},

//   { op: "replace", path: "/contactDetails/phoneNumbers/0/number", value: "123" },

//   { op: "add", path: "/contactDetails/phoneNumbers/1", value: {number:"456"}}

// ];

```



Example of generating patches with test operations for values in the first object:



```js

var document = { firstName: "Joachim", lastName: "Wester", contactDetails: { phoneNumbers: [ { number:"555-123" }] } };

var observer = jsonpatch.observe(document);

document.firstName = "Albert";

document.contactDetails.phoneNumbers[0].number = "123";

document.contactDetails.phoneNumbers.push({ number:"456" });

var patch = jsonpatch.generate(observer, true);

// patch  == [

//   { op: "test", path: "/firstName", value: "Joachim"},

//   { op: "replace", path: "/firstName", value: "Albert"},

//   { op: "test", path: "/contactDetails/phoneNumbers/0/number", value: "555-123" },

//   { op: "replace", path: "/contactDetails/phoneNumbers/0/number", value: "123" },

//   { op: "add", path: "/contactDetails/phoneNumbers/1", value: {number:"456"}}

// ];

```



#### `jsonpatch.unobserve(document, observer)`

```typescript

jsonpatch.unobserve(document: any, observer: Observer): void



type JsonableObj = { [key:string]: Jsonable };

type JsonableArr = Jsonable[];

type Jsonable = JsonableArr | JsonableObj | string | number | boolean | null;

```



Destroys the observer set up on `document`.



Any remaining changes are delivered synchronously (as in `jsonpatch.generate`). Note: this is different that ES6/7 `Object.unobserve`, which delivers remaining changes asynchronously.



#### `jsonpatch.compare(document1, document2, invertible)`



```typescript

jsonpatch.compare(document1: Jsonable, document2: Jsonable, invertible = false): Operation[]



type JsonableObj = { [key:string]: Jsonable };

type JsonableArr = Jsonable[];

type Jsonable = JsonableArr | JsonableObj | string | number | boolean | null;

```



Compares object trees `document1` and `document2` and returns the difference relative to `document1` as a patches array.  If `invertible` is true, then each change will be preceded by a test operation of the value in `document1`.



If there are no differences, returns an empty array (length 0).



Example:



```js

var documentA = {user: {firstName: "Albert", lastName: "Einstein"}};

var documentB = {user: {firstName: "Albert", lastName: "Collins"}};

var diff = jsonpatch.compare(documentA, documentB);

//diff == [{op: "replace", path: "/user/lastName", value: "Collins"}]

```



Example of comparing two object trees with test operations for values in the first object:



```js

var documentA = {user: {firstName: "Albert", lastName: "Einstein"}};

var documentB = {user: {firstName: "Albert", lastName: "Collins"}};

var diff = jsonpatch.compare(documentA, documentB, true);

//diff == [

//   {op: "test", path: "/user/lastName", value: "Einstein"},

//   {op: "replace", path: "/user/lastName", value: "Collins"}

// ];

```



#### `jsonpatch.validate(patch: Operation[], document?: any, validator?: Function): JsonPatchError`



See [Validation notes](#validation-notes)



Validates a sequence of operations. If `document` parameter is provided, the sequence is additionally validated against the object tree.



If there are no errors, returns undefined. If there is an errors, returns a JsonPatchError object with the following properties:



- `name` String - short error code

- `message` String - long human readable error message

- `index` Number - index of the operation in the sequence

- `operation` Object - reference to the operation

- `tree` Object - reference to the tree



Possible errors:



Error name                    | Error message

------------------------------|------------

SEQUENCE_NOT_AN_ARRAY         | Patch sequence must be an array

OPERATION_NOT_AN_OBJECT       | Operation is not an object

OPERATION_OP_INVALID          | Operation `op` property is not one of operations defined in RFC-6902

OPERATION_PATH_INVALID        | Operation `path` property is not a valid string

OPERATION_FROM_REQUIRED       | Operation `from` property is not present (applicable in `move` and `copy` operations)

OPERATION_VALUE_REQUIRED      | Operation `value` property is not present, or `undefined` (applicable in `add`, `replace` and `test` operations)

OPERATION_VALUE_CANNOT_CONTAIN_UNDEFINED  | Operation `value` property object has at least one `undefined` value (applicable in `add`, `replace` and `test` operations)

OPERATION_PATH_CANNOT_ADD     | Cannot perform an `add` operation at the desired path

OPERATION_PATH_UNRESOLVABLE   | Cannot perform the operation at a path that does not exist

OPERATION_FROM_UNRESOLVABLE   | Cannot perform the operation from a path that does not exist

OPERATION_PATH_ILLEGAL_ARRAY_INDEX | Expected an unsigned base-10 integer value, making the new referenced value the array element with the zero-based index

OPERATION_VALUE_OUT_OF_BOUNDS | The specified index MUST NOT be greater than the number of elements in the array

TEST_OPERATION_FAILED | When operation is `test` and the test fails, applies to `applyReducer`.



Example:



```js

var obj = {user: {firstName: "Albert"}};

var patches = [{op: "replace", path: "/user/firstName", value: "Albert"}, {op: "replace", path: "/user/lastName", value: "Einstein"}];

var errors = jsonpatch.validate(patches, obj);

if (errors.length == 0) {

 //there are no errors!

}

else {

  for (var i=0; i < errors.length; i++) {

    if (!errors[i]) {

      console.log("Valid patch at index", i, patches[i]);

    }

    else {

      console.error("Invalid patch at index", i, errors[i], patches[i]);

    }

  }

}

```



## `OperationResult` Type



Functions `applyPatch` and `applyOperation` both return `OperationResult` object. This object is:



```ts

{newDocument: any, test?: boolean, removed?: any}

```



Where:



- `newDocument`: the new state of the document after the patch/operation is applied.

- `test`: if the operation was a `test` operation. This will be its result.

- `removed`: contains the removed, moved, or replaced values from the document after a `remove`, `move` or `replace` operation.



## Validation Notes



Functions `applyPatch`, `applyOperation`, and `validate` accept a `validate`/ `validator` parameter:



- If the `validateOperation` parameter is set to `false`, validation will not occur.

- If set to `true`, the patch is extensively validated before applying using jsonpatch's default validation.

- If set to a `function` callback, the patch is validated using that function.



If you pass a validator, it will be called with four parameters for each operation, `function(operation, index, tree, existingPath)` and it is expected to throw `JsonPatchError` when your conditions are not met.



- `operation` The operation it self.

- `index` `operation`'s index in the patch array (if application).

- `tree` The object that is supposed to be patched.

- `existingPath` the path `operation` points to.



## Overwriting and `move` Operation



When the target of the move operation already exists, it is cached, deep cloned and returned as `removed` in `OperationResult`.



## `undefined`s (JS to JSON projection)



As `undefined` type does not exist in JSON, it's also not a valid value of JSON Patch operation. Therefore `jsonpatch` will not generate JSON Patches that sets anything to `undefined`.



Whenever a value is set to `undefined` in JS, JSON-Patch methods `generate` and `compare` will treat it similarly to how JavaScript method [`JSON.stringify` (MDN)](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify) treats them:



> If `undefined` (...) is encountered during conversion it is either omitted (when it is found in an object) or censored to `null` (when it is found in an array).



See the [ECMAScript spec](http://www.ecma-international.org/ecma-262/6.0/index.html#sec-json.stringify) for details.



## Specs/tests



 - [Run in browser](http://starcounter-jack.github.io/JSON-Patch/test/)



## [Contributing](CONTRIBUTING.md)



## Changelog



To see the list of recent changes, see [Releases](https://github.com/Starcounter-Jack/JSON-Patch/releases).



## Footprint

4 KB minified and gzipped (12 KB minified)



## Performance



##### [`add` benchmark](https://run.perf.zone/view/JSON-Patch-Add-Operation-1535541298893)



![image](https://user-images.githubusercontent.com/17054134/44784357-aa422480-ab8d-11e8-8a7e-037e692dd842.png)



##### [`replace` benchmark](https://run.perf.zone/view/JSON-Patch-Replace-Operation-1535540952263)



![image](https://user-images.githubusercontent.com/17054134/44784275-5fc0a800-ab8d-11e8-8a90-e87b8d5409d0.png)



Tested on 29.08.2018. Compared libraries:



- [Starcounter-Jack/JSON-Patch](https://www.npmjs.com/package/fast-json-patch) 2.0.6

- [bruth/jsonpatch-js](https://www.npmjs.com/package/json-patch) 0.7.0

- [dharmafly/jsonpatch.js](https://www.npmjs.com/package/jsonpatch) 3.0.1

- [jiff](https://www.npmjs.com/package/jiff) 0.7.3

- [RFC6902](https://www.npmjs.com/package/rfc6902) 2.4.0



We aim the tests to be fair. Our library puts performance as the #1 priority, while other libraries can have different priorities. If you'd like to update the benchmarks or add a library, please fork  the [perf.zone](https://perf.zone) benchmarks linked above and open an issue to include new results.



## License



MIT