Find differences in JS objects

deepDiffMapper

var deepDiffMapper = function() {
    return {
        VALUE_CREATED: 'created',
        VALUE_UPDATED: 'updated',
        VALUE_DELETED: 'deleted',
        VALUE_UNCHANGED: 'unchanged',
        map: function(obj1, obj2) {
            if (this.isFunction(obj1) || this.isFunction(obj2)) {
                throw 'Invalid argument. Function given, object expected.';
            }
            if (this.isValue(obj1) || this.isValue(obj2)) {
                //return {type: this.compareValues(obj1, obj2), data: obj1 || obj2};
                return this.compareValues(obj1, obj2);

            }
            
            var diff = {};
            for (var key in obj1) {
                if (this.isFunction(obj1[key])) {
                    continue;
                }
                
                var value2 = undefined;
                if ('undefined' != typeof(obj2[key])) {
                    value2 = obj2[key];
                }
                
                diff[key] = this.map(obj1[key], value2);
            }
            for (var key in obj2) {
                if (this.isFunction(obj2[key]) || ('undefined' != typeof(diff[key]))) {
                    continue;
                }
                
                diff[key] = this.map(undefined, obj2[key]);
            }
            
            return diff;
            
        },
        compareValues: function(value1, value2) {
            if (value1 === value2) {
                return this.VALUE_UNCHANGED;
            }
            if ('undefined' == typeof(value1)) {
                return this.VALUE_CREATED;
            }
            if ('undefined' == typeof(value2)) {
                return this.VALUE_DELETED;
            }
            return this.VALUE_UPDATED;
        },
        // use lodash functions
        isFunction: function(obj) {
            return toString.apply(obj) === '[object Function]';
        },
        isArray: function(obj) {
            return toString.apply(obj) === '[object Array]';
        },
        isObject: function(obj) {
            return toString.apply(obj) === '[object Object]';
        },
        isValue: function(obj) {
            return !this.isObject(obj) && !this.isArray(obj);
        }
    }
}();


var result = deepDiffMapper.map(
    {$$hashKey:'testId', obj1:'test', obj3:{test1:'test', test2:{a:1, b:2} } },
    {$$hashKey:'testId', obj1:'test', obj3:{test1:'test', test2:{a:1} } }
);
console.log(result);