add support for toJSON() js objects

.eslintrc

@@ -1,5 +1,6 @@
 env:
   node: true
+  mocha: true
 
 rules:
   # Possible Errors
@@ -45,7 +46,7 @@ rules:
   ## require parens for Constructor
   new-parens: 2
   ## max 80 length
-  max-len: [2, 80, 2]
+  max-len: [2, 120, 2]
   ## max 2 consecutive empty lines
   no-multiple-empty-lines: [2, {max: 2}]
   ## require newline at end of files

README.md

@@ -26,7 +26,7 @@ $ npm install json-merge-patch --save
 
 ## Usage
 
-Applying patches:
+### Applying patches:
 ```js
 var source = {
   "title": "Goodbye!",
@@ -53,7 +53,7 @@ var target = jsonmergepatch.apply(source, patch);
 // }
 ```
 
-Generating patches:
+### Generating patches:
 ```js
 var source = {
   "title": "Goodbye!",
@@ -72,6 +72,41 @@ var patch = jsonmergepatch.generate(source, target);
 // }
 ```
 
+
+### Usage with Javascript objects
+
+This library is primarily designed to work with JSON.
+Nonetheless, it is possible to use Javascript objects if the method `toJSON()` is implemented, the library will then serialize your object using it.
+```js
+var patch = jsonmergepatch.generate(
+  {
+    "title": "Goodbye!"
+  },
+  {
+    toJSON: () {
+      return {
+        "title": "I am serialized"
+      }
+    },
+  }
+);
+// patch = {
+// 	"title": "I am serialized",
+// }
+```
+
+```js
+var patch = jsonmergepatch.generate(
+  {},
+  {
+    date: new Date("2020-05-09T00:00:00.000")
+  }
+);
+// patch = {
+// 	date: "2020-05-09T00:00:00.000"
+// }
+```
+
 ## API
 
 #### jsonmergepatch.apply (`obj` Object, `patch` Object) : Object
@@ -87,10 +122,11 @@ Generates a `patch` Object from source and target Object.
 
 Generates a `patch` Object by merging patch1 and patch2.
 
+
 ## Running tests
 
 ```sh
-make test
+npm test
 ```
 
 # License

lib/apply.js

@@ -1,9 +1,14 @@
 'use strict';
 
+var serialize = require('./utils').serialize;
+
 module.exports = function apply(target, patch) {
+  patch = serialize(patch);
   if (patch === null || typeof patch !== 'object' || Array.isArray(patch)) {
     return patch;
   }
+
+  target = serialize(target);
   if (target === null || typeof target !== 'object' || Array.isArray(target)) {
     target = {};
   }

lib/generate.js

@@ -1,6 +1,7 @@
 'use strict';
 
 var equal = require('deep-equal');
+var serialize = require('./utils').serialize;
 
 function arrayEquals(before, after) {
   if (before.length !== after.length) {
@@ -15,6 +16,9 @@ function arrayEquals(before, after) {
 }
 
 module.exports = function generate(before, after) {
+  before = serialize(before);
+  after = serialize(after);
+
   if (before === null || after === null ||
     typeof before !== 'object' || typeof after !== 'object' ||
     Array.isArray(before) !== Array.isArray(after)) {
@@ -40,7 +44,7 @@ module.exports = function generate(before, after) {
     key = afterKeys[i];
     if (beforeKeys.indexOf(key) === -1) {
       newKeys[key] = true;
-      patch[key] = after[key];
+      patch[key] = serialize(after[key]);
     }
   }
 
@@ -58,7 +62,7 @@ module.exports = function generate(before, after) {
           patch[key] = subPatch;
         }
       } else if (before[key] !== after[key]) {
-        patch[key] = after[key];
+        patch[key] = serialize(after[key]);
       }
     }
   }

lib/utils.js

@@ -0,0 +1,5 @@
+'use strict';
+
+module.exports.serialize = function(value) {
+  return (value && typeof value.toJSON === 'function') ? value.toJSON() : value;
+};

test/lib/apply.js

@@ -5,108 +5,115 @@ var assert = require('chai').assert;
 var apply = require('../../lib/apply');
 
 describe('apply', function() {
-	it('should replace an attribute', function() {
-		assert.deepEqual(
-			apply({a: 'b'}, {a: 'c'}),
+  it('should replace an attribute', function() {
+    assert.deepEqual(
+      apply({a: 'b'}, {a: 'c'}),
 	    {a: 'c'}
     );
-	});
+  });
 
-	it('should add an attribute', function() {
-		assert.deepEqual(
-			apply({a: 'b'}, {b: 'c'}),
+  it('should add an attribute', function() {
+    assert.deepEqual(
+      apply({a: 'b'}, {b: 'c'}),
 	    {a: 'b', b: 'c'}
     );
-	});
+  });
 
-	it('should delete attribute', function() {
-		assert.deepEqual(
-			apply({a: 'b'}, {a: null}),
+  it('should delete attribute', function() {
+    assert.deepEqual(
+      apply({a: 'b'}, {a: null}),
 	    {}
     );
-	});
+  });
 
-	it('should delete attribute without affecting others', function() {
-		assert.deepEqual(
-			apply({a: 'b', b: 'c'}, {a: null}),
+  it('should delete attribute without affecting others', function() {
+    assert.deepEqual(
+      apply({a: 'b', b: 'c'}, {a: null}),
 	    {b: 'c'}
     );
-	});
+  });
 
-	it('should replace array with a string', function() {
-		assert.deepEqual(
-			apply({a: ['b']}, {a: 'c'}),
+  it('should replace array with a string', function() {
+    assert.deepEqual(
+      apply({a: ['b']}, {a: 'c'}),
 	    {a: 'c'}
     );
-	});
+  });
 
-	it('should replace an string with an array', function() {
-		assert.deepEqual(
-			apply({a: 'c'}, {a: ['b']}),
+  it('should replace an string with an array', function() {
+    assert.deepEqual(
+      apply({a: 'c'}, {a: ['b']}),
 	    {a: ['b']}
     );
-	});
+  });
 
-	it('should apply recursively', function() {
-		assert.deepEqual(
-			apply({a: {b: 'c'}}, {a: {b: 'd', c: null}}),
+  it('should apply recursively', function() {
+    assert.deepEqual(
+      apply({a: {b: 'c'}}, {a: {b: 'd', c: null}}),
 	    {a: {b: 'd'}}
     );
-	});
+  });
 
-	it('should replace an object array with a number array', function() {
-		assert.deepEqual(
-			apply({a: [{b: 'c'}]}, {a: [1]}),
+  it('should replace an object array with a number array', function() {
+    assert.deepEqual(
+      apply({a: [{b: 'c'}]}, {a: [1]}),
 	    {a: [1]}
     );
-	});
+  });
 
-	it('should replace an array', function() {
-		assert.deepEqual(
-			apply(['a', 'b'], ['c', 'd']),
-			['c', 'd']
+  it('should replace an array', function() {
+    assert.deepEqual(
+      apply(['a', 'b'], ['c', 'd']),
+      ['c', 'd']
     );
-	});
+  });
 
-	it('should replace an object with an array', function() {
-		assert.deepEqual(
-			apply({a: 'b'}, ['c']),
-			['c']
+  it('should replace an object with an array', function() {
+    assert.deepEqual(
+      apply({a: 'b'}, ['c']),
+      ['c']
     );
-	});
+  });
 
-	it('should replace an object with null', function() {
-		assert.deepEqual(
-			apply({a: 'foo'}, null),
-			null
+  it('should replace an object with null', function() {
+    assert.deepEqual(
+      apply({a: 'foo'}, null),
+      null
     );
-	});
+  });
 
-	it('should replace an object with a string', function() {
-		assert.deepEqual(
-			apply({a: 'foo'}, 'bar'),
-			'bar'
+  it('should replace with an object implementing toJSON() method', function() {
+    assert.deepEqual(
+      apply({a: 'foo'}, {a: new Date('2020-05-09T00:00:00.000Z')}),
+      {a: '2020-05-09T00:00:00.000Z'}
     );
-	});
+  });
 
-	it('should not change null attributes', function() {
-		assert.deepEqual(
-			apply({e: null}, {a: 1}),
-			{e: null, a: 1}
+  it('should replace an object with a string', function() {
+    assert.deepEqual(
+      apply({a: 'foo'}, 'bar'),
+      'bar'
     );
-	});
+  });
 
-	it('should not set an attribute to null', function() {
-		assert.deepEqual(
-			apply([1, 2], {a: 'b', c: null}),
-			{a: 'b'}
+  it('should not change null attributes', function() {
+    assert.deepEqual(
+      apply({e: null}, {a: 1}),
+      {e: null, a: 1}
     );
-	});
+  });
 
-	it('should not set an attribute to null in a sub object', function() {
-		assert.deepEqual(
-			apply({}, {a: {bb: {ccc: null}}}),
-			{a: {bb: {}}}
-		);
-	});
+  it('should not set an attribute to null', function() {
+    assert.deepEqual(
+      apply([1, 2], {a: 'b', c: null}),
+      {a: 'b'}
+    );
+  });
+
+  it('should not set an attribute to null in a sub object', function() {
+    assert.deepEqual(
+      apply({}, {a: {bb: {ccc: null}}}),
+      {a: {bb: {}}}
+    );
+  });
 });