手写实现深拷贝一解决循环引用问题

function deepClone(source, clonedMap = new Map()) {
  if(typeof source !== "object" || source == null){
    return source;
  }

  // 如果这个对象已经被拷贝过，直接从Map中返回
  if(clonedMap.has(source)){
    return clonedMap.get(source);
  }

  const target = Array.isArray(source) ? [] : {};

  // 在Map中记录这个对象
  clonedMap.set(source, target);

  for(const key in source){
    if( typeof source[key] === "object" && source[key] !== null){
      target[key] = deepClone(source[key], clonedMap);
    } else {
      target[key] = source[key];
    }
  }
  return target;
}

const obj = {a: 1, b: {c: 2}}
obj.self = obj;

const copy = deepClone(obj);

console.log(copy);
//{ a: 1, b: { c: 2 }, self: [Circular] }