通过从现有对象中获取一些元素来创建新对象

let originalObj = { a: 1, b: { c: 2 } };
let shallowCopy = { ...originalObj };

shallowCopy.a = 10;
shallowCopy.b.c = 20;

console.log(originalObj); // { a: 1, b: { c: 20 } }

let originalObj = { a: 1, b: { c: 2 } };
let deepCopy = JSON.parse(JSON.stringify(originalObj));

deepCopy.a = 10;
deepCopy.b.c = 20;

console.log(originalObj); // { a: 1, b: { c: 2 } }

function deepClone(obj, hash = new WeakMap()) {
  if (obj === null || typeof obj !== 'object') return obj;
  if (hash.has(obj)) return hash.get(obj);

  let cloneObj = Array.isArray(obj) ? [] : {};
  hash.set(obj, cloneObj);

  for (let key in obj) {
    if (obj.hasOwnProperty(key)) {
      cloneObj[key] = deepClone(obj[key], hash);
    }
  }

  return cloneObj;
}

let originalObj = { a: 1 };
originalObj.b = originalObj;

let deepCopy = deepClone(originalObj);
console.log(deepCopy); // { a: 1, b: [Circular] }