add patches merging

Author: pierreinglebert

README.md

@@ -80,6 +80,11 @@ Applies `patch` on `obj`.
 
 Generates a `patch` Object from source and target Object.
 
+
+#### jsonmergepatch.merge (`patch1` Object, `patch2` Object) : `patch` Object
+
+Generates a `patch` Object by merging patch1 and patch2.
+
 ## Running tests
 
 ```sh

lib/merge.js

@@ -0,0 +1,20 @@
+'use strict';
+
+module.exports = function merge(patch1, patch2) {
+ if(patch1 === null || patch2 === null ||
+ typeof patch1 !== 'object' || typeof patch2 !== 'object' ||
+ Array.isArray(patch1) !== Array.isArray(patch2)) {
+ return patch2;
+ }
+ var patch = JSON.parse(JSON.stringify(patch1));
+
+Object.keys(patch2)
+ .forEach(function(key) {
+if(patch1[key] !== undefined) {
+ patch[key] = merge(patch1[key], patch2[key]);
+} else {
+patch[key] = patch2[key];
+}
+ });
+return patch;
+};

test/lib/merge.js

@@ -0,0 +1,85 @@
+'use strict';
+
+var assert = require('chai').assert;
+
+var merge = require('../../lib/merge');
+
+describe('merge', function() {
+
+it('should merge 2 patches with different attributes', function() {
+assert.deepEqual(
+merge({a: 'b'}, {b: 'c'}),
+ {a: 'b', b: 'c'}
+ );
+});
+
+it('should merge take last patch attributes for rewriting', function() {
+assert.deepEqual(
+merge({a: 'b'}, {a: 'c'}),
+{a: 'c'}
+ );
+});
+
+it('should merge take last patch attributes for rewriting and keep other attributes', function() {
+assert.deepEqual(
+merge({a: 'b', b: 'd'}, {a: 'c'}),
+{a: 'c', b: 'd'}
+ );
+});
+
+it('should keep null attributes for deleting', function() {
+assert.deepEqual(
+merge({a: null}, {b: 'c'}),
+{a: null, b: 'c'}
+ );
+});
+
+it('should replace null with newer attribute', function() {
+assert.deepEqual(
+merge({a: null}, {a: 'b'}),
+{a: 'b'}
+);
+});
+
+it('should replace an attribute with null if newer', function() {
+assert.deepEqual(
+merge({a: 'b'}, {a: null}),
+{a: null}
+);
+});
+
+it('should replace an array with an object', function() {
+assert.deepEqual(
+merge([], {a: 'b'}),
+{a: 'b'}
+);
+});
+
+it('should replace an object with an array', function() {
+assert.deepEqual(
+merge({a: 'b'}, []),
+[]
+);
+});
+
+it('should merge sub objects', function() {
+assert.deepEqual(
+merge({a: {b: {c: 'd'}}, d: 'e'}, {a: {b: 'a'}}),
+{a: {b: 'a'}, d: 'e'}
+);
+});
+
+it('should merge recursively', function() {
+assert.deepEqual(
+merge({a: {b: {c: 'd'}, d: 'e'}}, {a: {b: {c: 'e'}}}),
+{a: {b: {c: 'e'}, d: 'e'}}
+);
+});
+
+it('should replace object with with null value', function() {
+assert.deepEqual(
+merge({a: 'b'}, null),
+null
+);
+});
+});