comparator for custom equality checks

README.md

@@ -63,6 +63,9 @@ bower install jsdiff --save
 
 * `JsDiff.diffArrays(oldArr, newArr[, options])` - diffs two arrays, comparing each item for strict equality (===).
 
+    Options
+    * `comparator`: `function(left, right)` for custom equality checks
+
     Returns a list of change objects (See below).
 
 * `JsDiff.createTwoFilesPatch(oldFileName, newFileName, oldStr, newStr, oldHeader, newHeader)` - creates a unified diff patch.

src/diff/base.js

@@ -144,8 +144,15 @@ Diff.prototype = {
   },
 
   equals(left, right) {
-    return left === right
-      || (this.options.ignoreCase && left.toLowerCase() === right.toLowerCase());
+    if (this.options.comparator) {
+      if (Array.isArray(right)) {
+        right = right[0];
+      }
+      return this.options.comparator(left, right);
+    } else {
+      return left === right
+        || (this.options.ignoreCase && left.toLowerCase() === right.toLowerCase());
+    }
   },
   removeEmpty(array) {
     let ret = [];

test/diff/array.js

@@ -15,5 +15,20 @@ describe('diff/array', function() {
           {count: 1, value: [c], removed: true, added: undefined}
       ]);
     });
+
+    it('Should diff arrays with comparator', function() {
+      const a = {a: 0}, b = {a: 1}, c = {a: 2}, d = {a: 3};
+      function comparator(left, right) {
+        return left.a === right.a;
+      }
+      const diffResult = diffArrays([a, b, c], [a, b, d], { comparator: comparator });
+      console.log(diffResult);
+      expect(diffResult).to.deep.equals([
+          {count: 2, value: [a, b]},
+          {count: 1, value: [c], removed: true, added: undefined},
+          {count: 1, value: [d], removed: undefined, added: true}
+      ]);
+    });
+
   });
 });