Add undefinedReplacement option to diffJson

Author: ewnd9

Diff for: src/diff/json.js

@@ -11,14 +11,33 @@ jsonDiff.useLongestToken = true;
 
 jsonDiff.tokenize = lineDiff.tokenize;
 jsonDiff.castInput = function(value) {
-  return typeof value === 'string' ? value : JSON.stringify(canonicalize(value), undefined, '  ');
+  const {undefinedReplacement} = this;
+
+  return typeof value === 'string' ? value : JSON.stringify(canonicalize(value), function(k, v) {
+    if (typeof v === 'undefined') {
+      return undefinedReplacement;
+    }
+
+    return v;
+  }, '  ');
 };
 jsonDiff.equals = function(left, right) {
   return Diff.prototype.equals(left.replace(/,([\r\n])/g, '$1'), right.replace(/,([\r\n])/g, '$1'));
 };
 
-export function diffJson(oldObj, newObj, callback) { return jsonDiff.diff(oldObj, newObj, callback); }
+export function diffJson(oldObj, newObj, options, callback) {
+  if (typeof options === 'function') {
+    callback = options;
+    options = {};
+  }
 
+  if (typeof options === 'undefined') {
+    options = {};
+  }
+
+  jsonDiff.undefinedReplacement = options.undefinedReplacement;
+  return jsonDiff.diff(oldObj, newObj, callback);
+}
 
 // This function handles the presence of circular references by bailing out when encountering an
 // object that is already on the "stack" of items being processed.

Diff for: test/diff/json.js

@@ -66,6 +66,27 @@ describe('diff/json', function() {
       )).to.eql([
         { count: 4, value: '{\n  "a": 123,\n  "b": 456\n}' }
       ]);
+      expect(diffJson(
+        {a: 123, b: 456, c: undefined},
+        {a: 123, b: 456},
+        {undefinedReplacement: null}
+      )).to.eql([
+        { count: 3, value: '{\n  "a": 123,\n  "b": 456,\n' },
+        { count: 1, value: '  "c": null\n', added: undefined, removed: true },
+        { count: 1, value: '}' }
+      ]);
+    });
+
+    it('should handle callback', function(done) {
+      diffJson(
+        {},
+        {},
+        function(err, result) {
+          expect(err).to.be.undefined;
+          expect(result).to.eql([{ count: 1, value: '{}' }]);
+          done();
+        }
+      );
     });
 
     it('should accept already stringified JSON', function() {