json-touch-patch


> Immutable JSON Patch implementation based on RFC 6902

Features

- Immutable: The original JSON is not update. The patches apply to a new JSON.
- Touch: The patches create a new object if it includes some changes into child elements.
- Rollback: If error occurs, all patches are rejected. Return the original JSON.
- Customizable: You can add custom operator using the operator API. → Wiki
- Maybe, these features are suitable to operate store in React and Redux architecture.

Installation

``
$ npm install --save json-touch-patch
`

API

- patch(prevObject: object, patches: object[], [ opts: object ]): object
- opts.custom: object custom operator definition.
- opts.partial: boolean not reject patches if error occurs (partial patching)
- opts.strict: boolean throw an exception if error occurs
- opts.error: object point to a cause patch if error occurs
- returns nextObject: object

Quick example

`js
const patch = require("json-touch-patch");

const prevObject = { "baz": "qux", "foo": "bar" };
const patches = [
{ "op": "replace", "path": "/baz", "value": "boo" },
];
const nextObject = patch(prevObject, patches);
// → { "baz": "boo", "foo": "bar" }
// |
// replaced

console.log(prevObject);
// → { "baz": "qux", "foo": "bar" }
// |
// not changed
`

How to apply patches

$3

`js
const patches = [
{ op: "add", path: "/matrix/1/-", value: 9 },
];
`

Return a new JSON. It contains shallow-copied elements that have some changes into child elements. And it contains original elements that are not updated any.

!add

`js
assert(prevObject.matrix[0] === nextObject.matrix[0]);
assert(prevObject.matrix[1] !== nextObject.matrix[1]);
assert(prevObject.matrix[2] === nextObject.matrix[2]);
`

$3

`js
const patches = [
{ op: "remove", path: "/matrix/1" },
];
`

Return a new JSON. It contains shallow-copied elements that have some changes into child elements. And it contains original elements that are not updated any.

!remove

`js
assert(prevObject.matrix[0] === nextObject.matrix[0]);
assert(prevObject.matrix[1] !== nextObject.martix[1]);
assert(prevObject.matrix[2] === nextObject.matrix[1]);
`

$3

`js
const patches = [
{ op: "replace", path: "/matrix/1/1", value: 9 },
];
`

Return a new JSON. It contains shallow-copied elements that have some changes into child elements. And it contains original elements that are not updated any.

!replace

`js
assert(prevObject.matrix[0] === nextObject.matrix[0]);
assert(prevObject.matrix[1] !== nextObject.matrix[1]);
assert(prevObject.matrix[2] === nextObject.matrix[2]);
`

$3

`js
const patches = [
{ op: "replace", path: "/matrix/1/1", value: 4 },
];
`

Return the original JSON. Because all elements are not changed.

!replace

prevObject.matrix[1][1] is already 4. So, this patch is need not to update any.

`js
assert(prevObject === nextObject);
`

$3

`js
const patches = [
{ op: "move", from: "/matrix/1", path: "/matrix/2" },
];
`

Return a new JSON. [op:move] works as [op:get(from)] -> [op:remove(from)] -> [op:add(path)].

!move

`js
assert(prevObject.matrix[0] === nextObject.matrix[0]);
assert(prevObject.matrix[1] === nextObject.martix[2]);
assert(prevObject.matrix[2] === nextObject.matrix[1]);
`

$3

`js
const patches = [
{ op: "copy", from: "/matrix/1", path: "/matrix/1" },
];
`

Return a new JSON. [op:copy] works as [op:get(from)] -> [op:add(path)].

!copy

`js
assert(prevObject.matrix[0] === nextObject.matrix[0]);
assert(prevObject.matrix[1] === nextObject.martix[1]);
assert(prevObject.matrix[1] === nextObject.martix[2]);
assert(prevObject.matrix[2] === nextObject.matrix[3]);
`

$3

`js
const patch = [
{ op: "add" , path: "/matrix/1/-", value: 9 },
{ op: "test", path: "/matrix/1/1", value: 0 },
];
`

Return the original JSON. Because a test op is failed. All patches are rejected.

!test

prevObject.matrix[1][1] is not 0 but 4. So, this test is failed.

`js
assert(prevObject === nextObject);
`

$3

`js
const json = [
{ op: "replace", path: "/matrix/1/100", value: 9 },
];
`

Return the original JSON. Because all patches are rejected when error occurs.

!invalid

prevObject.matrix[1][100] is not defined. So, this patch is invalid.

`js
assert(prevObject === nextObject);
``

License

MIT