javascript 深拷贝

//isActiveClone防止循环引用
function clone(obj) {
    if (obj === null || typeof obj !== 'object' || 'isActiveClone' in obj) {
        return obj;
    }

    var temp = obj.constructor(); //使temp的prototype与obj的相同

    for (var key in obj) {
        if (Object.prototype.hasOwnProperty.call(obj, key)) {
            obj['isActiveClone'] = null;
            temp[key] = clone(obj[key]);
            delete obj['isActiveClone'];
        }
    }
    return temp;
}