function deepEqualCyclic(obj1, obj2) {

        // used for cyclic comparison
        // contain already visited objects
        var objects1 = [],
            objects2 = [],
        // contain pathes (position in the object structure)
        // of the already visited objects
        // indexes same as in objects arrays
            paths1 = [],
            paths2 = [],
        // contains combinations of already compared objects
        // in the manner: { "$1['ref']$2['ref']": true }
            compared = {};

        /**
         * used to check, if the value of a property is an object
         * (cyclic logic is only needed for objects)
         * only needed for cyclic logic
         */
        function isObject(value) {

            if (typeof value === 'object' && value !== null &&
                    !(value instanceof Boolean) &&
                    !(value instanceof Date)    &&
                    !(value instanceof Number)  &&
                    !(value instanceof RegExp)  &&
                    !(value instanceof String)) {

                return true;
            }

            return false;
        }

        /**
         * returns the index of the given object in the
         * given objects array, -1 if not contained
         * only needed for cyclic logic
         */
        function getIndex(objects, obj) {

            var i;
            for (i = 0; i < objects.length; i++) {
                if (objects[i] === obj) {
                    return i;
                }
            }

            return -1;
        }

        // does the recursion for the deep equal check
        return (function deepEqual(obj1, obj2, path1, path2) {
            var type1 = typeof obj1;
            var type2 = typeof obj2;

            // == null also matches undefined
            if (obj1 === obj2 ||
                    isNaN(obj1) || isNaN(obj2) ||
                    obj1 == null || obj2 == null ||
                    type1 !== "object" || type2 !== "object") {

                return identical(obj1, obj2);
            }

            // Elements are only equal if identical(expected, actual)
            if (isElement(obj1) || isElement(obj2)) { return false; }

            var isDate1 = isDate(obj1), isDate2 = isDate(obj2);
            if (isDate1 || isDate2) {
                if (!isDate1 || !isDate2 || obj1.getTime() !== obj2.getTime()) {
                    return false;
                }
            }

            if (obj1 instanceof RegExp && obj2 instanceof RegExp) {
                if (obj1.toString() !== obj2.toString()) { return false; }
            }

            var class1 = getClass(obj1);
            var class2 = getClass(obj2);
            var keys1 = keys(obj1);
            var keys2 = keys(obj2);

            if (isArguments(obj1) || isArguments(obj2)) {
                if (obj1.length !== obj2.length) { return false; }
            } else {
                if (type1 !== type2 || class1 !== class2 ||
                        keys1.length !== keys2.length) {
                    return false;
                }
            }

            var key, i, l,
                // following vars are used for the cyclic logic
                value1, value2,
                isObject1, isObject2,
                index1, index2,
                newPath1, newPath2;

            for (i = 0, l = keys1.length; i < l; i++) {
                key = keys1[i];
                if (!o.hasOwnProperty.call(obj2, key)) {
                    return false;
                }

                // Start of the cyclic logic

                value1 = obj1[key];
                value2 = obj2[key];

                isObject1 = isObject(value1);
                isObject2 = isObject(value2);

                // determine, if the objects were already visited
                // (it's faster to check for isObject first, than to
                // get -1 from getIndex for non objects)
                index1 = isObject1 ? getIndex(objects1, value1) : -1;
                index2 = isObject2 ? getIndex(objects2, value2) : -1;

                // determine the new pathes of the objects
                // - for non cyclic objects the current path will be extended
                //   by current property name
                // - for cyclic objects the stored path is taken
                newPath1 = index1 !== -1
                    ? paths1[index1]
                    : path1 + '[' + JSON.stringify(key) + ']';
                newPath2 = index2 !== -1
                    ? paths2[index2]
                    : path2 + '[' + JSON.stringify(key) + ']';

                // stop recursion if current objects are already compared
                if (compared[newPath1 + newPath2]) {
                    return true;
                }

                // remember the current objects and their pathes
                if (index1 === -1 && isObject1) {
                    objects1.push(value1);
                    paths1.push(newPath1);
                }
                if (index2 === -1 && isObject2) {
                    objects2.push(value2);
                    paths2.push(newPath2);
                }

                // remember that the current objects are already compared
                if (isObject1 && isObject2) {
                    compared[newPath1 + newPath2] = true;
                }

                // End of cyclic logic

                // neither value1 nor value2 is a cycle
                // continue with next level
                if (!deepEqual(value1, value2, newPath1, newPath2)) {
                    return false;
                }
            }

            return true;

        }(obj1, obj2, '$1', '$2'));
    }
@name samsam.deepEqual
@param Object obj1
@param Object obj2

Deep equal comparison. Two values are "deep equal" if:

  - They are equal, according to samsam.identical
  - They are both date objects representing the same time
  - They are both arrays containing elements that are all deepEqual
  - They are objects with the same set of properties, and each property
    in ``obj1`` is deepEqual to the corresponding property in ``obj2``

Supports cyclic objects.