function deepClone(obj, map = new WeakMap()) {
    if (obj === null || typeof obj !== 'object') return obj;
    if (map.has(obj)) return map.get(obj);            // 解决循环引用
    const clone = Array.isArray(obj) ? [] : {};
    map.set(obj, clone);
    for (const key of Object.keys(obj)) {
        clone[key] = deepClone(obj[key], map);
    }
    return clone;
}