JSON-Patch
===============
> A leaner and meaner implementation of JSON-Patch. Small footprint. High performance.
[](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
```
### 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)
##### [`replace` benchmark](https://run.perf.zone/view/JSON-Patch-Replace-Operation-1535540952263)
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