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JSON Diff and Patch

Jiff is an implementation of JSON Patch RFC6902, plus a Diff implementation that generates compliant patches.

It handles nuances of the RFC, such as:

  1. Checking for invalid paths in all operations
  2. Allowing add to behave like replace for existing paths (See bullet 3)
  3. Appending to arrays when path ends with "/-" (See bullet 6)
  4. Validating array indices obey JSON Pointer rules
  5. Allowing add and replace to replace the whole document when path is ""
  6. Deep comparisons for the test operation regardless of object key order (eg, if JSON documents were serialized using different key ordering algorithms)

Get it

npm install --save jiff

bower install --save jiff

Example

var a = [
	{ name: 'a' },
	{ name: 'b' },
	{ name: 'c' },
]

var b = a.slice();
b.splice(1, 1);
b.push({ name: 'd' });

// Generate diff (ie JSON Patch) from a to b
var patch = jiff.diff(a, b);

// [{"op":"add","path":"/3","value":{"name":"d"}},{"op":"remove","path":"/1"}]
console.log(JSON.stringify(patch));

var patched = jiff.patch(patch, a);

// [{"name":"a"},{"name":"c"},{"name":"d"}]
console.log(JSON.stringify(patched);

API

patch

var b = jiff.patch(patch, a);

Given an rfc6902 JSON Patch, apply it to a and return a new patched JSON object/array/value. Patching is atomic, and is performed on a clone of a. Thus, if patching fails mid-patch, a will still be in a consistent state.

Throws InvalidPatchOperationError and TestFailedError.

patchInPlace

a = jiff.patchInPlace(patch, a);

Given an rfc6902 JSON Patch, apply it directly to a, mutating a.

Note that this is an opt-in violation of the patching algorithm outlined in rfc6902. It may provide some performance benefits as it avoids creating a new clone of a before patching.

However, if patching fails mid-patch, a will be left in an inconsistent state.

Throws InvalidPatchOperationError and TestFailedError.

diff

var patch = jiff.diff(a, b [, hashFunction]);

Computes and returns a JSON Patch from a to b: a and b must be valid JSON objects/arrays/values of the same type. If patch is applied to a, it will yield b.

If provided, the optional hashFunction will be used to recognize when two objects are the same. If not provided, JSON.stringify will be used.

While jiff's patch algorithm handles all the JSON Patch operations required by rfc6902, the diff algorithm currently does not generate move, or copy operations, only add, remove, and replace.

clone

var b = jiff.clone(a);

Creates a deep copy of a, which must be a valid JSON object/array/value.

InvalidPatchOperationError

Thrown when any invalid patch operation is encountered. Invalid patch operations are outlined in sections 4.x and 5 in rfc6902. For example: non-existent path in a remove operation, array path index out of bounds, etc.

TestFailedError

Thrown when a test operation fails.

License

MIT