Add support for symbols to _.clone, _.cloneDeep, and _.isEqual.

lodash.js

@@ -80,6 +80,7 @@
       regexpTag = '[object RegExp]',
       setTag = '[object Set]',
       stringTag = '[object String]',
+      symbolTag = '[object Symbol]',
       weakMapTag = '[object WeakMap]';
 
   var arrayBufferTag = '[object ArrayBuffer]',
@@ -253,8 +254,9 @@
   cloneableTags[mapTag] = cloneableTags[numberTag] =
   cloneableTags[objectTag] = cloneableTags[regexpTag] =
   cloneableTags[setTag] = cloneableTags[stringTag] =
-  cloneableTags[uint8Tag] = cloneableTags[uint8ClampedTag] =
-  cloneableTags[uint16Tag] = cloneableTags[uint32Tag] = true;
+  cloneableTags[symbolTag] = cloneableTags[uint8Tag] =
+  cloneableTags[uint8ClampedTag] = cloneableTags[uint16Tag] =
+  cloneableTags[uint32Tag] = true;
   cloneableTags[errorTag] = cloneableTags[funcTag] =
   cloneableTags[weakMapTag] = false;
 
@@ -1458,6 +1460,9 @@
     var mapCtorString = Map ? fnToString.call(Map) : '',
         setCtorString = Set ? fnToString.call(Set) : '';
 
+    /** Used to convert symbols to strings. */
+    var symbolToString = Symbol ? Symbol.prototype.toString : undefined;
+
     /** Used to lookup unminified function names. */
     var realNames = {};
 
@@ -2772,7 +2777,10 @@
       if (value === other) {
         return true;
       }
-      if (value == null || other == null || (!isObject(value) && !isObjectLike(other))) {
+      if (value == null || other == null || (
+            !(typeof value == 'symbol' || isObject(value)) &&
+            !(typeof other == 'symbol' || isObjectLike(other))
+          )) {
         return value !== value && other !== other;
       }
       return baseIsEqualDeep(value, other, baseIsEqual, customizer, bitmask, stack);
@@ -3750,6 +3758,20 @@
       return arrayReduce(setToArray(set), addSetEntry, new Ctor);
     }
 
+    /**
+     * Creates a clone of `symbol`.
+     *
+     * @private
+     * @param {Object} symbol The symbol to clone.
+     * @returns {Object} Returns the cloned symbol.
+     */
+    function cloneSymbol(symbol) {
+      var Ctor = symbol.constructor,
+          result = Ctor(symbolToString.call(symbol).slice(7, -1));
+
+      return typeof symbol == 'object' ? Object(result) : result;
+    }
+
     /**
      * Creates a clone of `typedArray`.
      *
@@ -4519,6 +4541,9 @@
           // Recursively compare objects (susceptible to call stack limits).
           return (isPartial || object.size == other.size) &&
             equalFunc(convert(object), convert(other), customizer, bitmask | UNORDERED_COMPARE_FLAG);
+
+        case symbolTag:
+          return symbolToString.call(object) == symbolToString.call(other);
       }
       return false;
     }
@@ -4831,11 +4856,14 @@
         case stringTag:
           return new Ctor(object);
 
+        case regexpTag:
+          return cloneRegExp(object);
+
         case setTag:
           return cloneSet(object);
 
-        case regexpTag:
-          return cloneRegExp(object);
+        case symbolTag:
+          return cloneSymbol(object);
       }
     }
 

test/test.js

@@ -2199,6 +2199,9 @@
       set.add(1);
       set.add(2);
     }
+    if (Symbol) {
+      var symbol = Symbol('a');
+    }
     var objects = {
       '`arguments` objects': arguments,
       'arrays': ['a', ''],
@@ -2217,6 +2220,7 @@
       'sets': set,
       'strings': 'a',
       'string objects': Object('a'),
+      'symbols': symbol,
       'undefined values': undefined
     };
 
@@ -2309,12 +2313,14 @@
         QUnit.test('`_.' + methodName + '` should clone ' + key, function(assert) {
           assert.expect(2);
 
-          var isEqual = (key == 'maps' || key == 'sets') ? _.isEqual : lodashStable,
+          var useUnstable = /^(?:maps|sets|symbols)$/.test(key),
+              isEqual = useUnstable ? _.isEqual : lodashStable.isEqual,
+              isObject = useUnstable ? _.isObject : lodashStable.isObject,
               actual = func(object);
 
           assert.ok(isEqual(actual, object));
 
-          if (lodashStable.isObject(object)) {
+          if (isObject(object)) {
             assert.notStrictEqual(actual, object);
           } else {
             assert.strictEqual(actual, object);
@@ -2358,6 +2364,22 @@
         assert.strictEqual(actual.lastIndex, 3);
       });
 
+      QUnit.test('`_.' + methodName + '` should clone symbol objects', function(assert) {
+        assert.expect(3);
+
+        if (Symbol) {
+          var object = Object(symbol),
+              actual = func(object);
+
+          assert.strictEqual(typeof actual, 'object');
+          assert.strictEqual(typeof actual.valueOf(), 'symbol');
+          assert.notStrictEqual(actual, object);
+        }
+        else {
+          skipTest(assert, 3);
+        }
+      });
+
       QUnit.test('`_.' + methodName + '` should not error on DOM elements', function(assert) {
         assert.expect(1);
 
@@ -8113,6 +8135,30 @@
       }
     });
 
+    QUnit.test('should compare symbols', function(assert) {
+      assert.expect(4);
+
+      if (Symbol) {
+        var symbol1 = Symbol('a'),
+            symbol2 = Symbol('b');
+
+        assert.strictEqual(_.isEqual(symbol1, symbol2), false);
+
+        symbol2 = Symbol('a');
+        assert.strictEqual(_.isEqual(symbol1, symbol2), true);
+
+        symbol1 = Symbol(undefined);
+        symbol2 = Symbol('');
+        assert.strictEqual(_.isEqual(symbol1, symbol2), true);
+
+        symbol1 = Symbol(null);
+        assert.strictEqual(_.isEqual(symbol1, symbol2), false);
+      }
+      else {
+        skipTest(assert, 4);
+      }
+    });
+
     QUnit.test('should compare typed arrays', function(assert) {
       assert.expect(1);
 
@@ -9452,7 +9498,7 @@
     var args = arguments;
 
     QUnit.test('should return `true` for objects', function(assert) {
-      assert.expect(12);
+      assert.expect(13);
 
       assert.strictEqual(_.isObject(args), true);
       assert.strictEqual(_.isObject([1, 2, 3]), true);
@@ -9468,7 +9514,14 @@
 
       if (document) {
         assert.strictEqual(_.isObject(body), true);
-      } else {
+      }
+      else {
+        skipTest(assert);
+      }
+      if (Symbol) {
+        assert.strictEqual(_.isObject(Object(Symbol())), true);
+      }
+      else {
         skipTest(assert);
       }
     });