Several ways to implement deep copy in js

1. Recursive implementation

Recursive implementation is the most basic deep copy method. It traverses object properties, and if the property itself is a reference type, it continues to recursively copy.

function deepClone(obj) {
  if (obj === null || typeof obj !== 'object') return obj;
  const clone = Array.isArray(obj) ? [] : {};
  for (let key in obj) {
    clone[key] = deepClone(obj[key]);
  }
  return clone;
}

2. JSON implementation

JSON.parse and JSON.stringify provide deep copy functions, but only for data types that support serialization and deserialization, such as basic data types and some object types.

function deepClone(obj) {
  return JSON.parse(JSON.stringify(obj));
}

3. Object.assign implementation

Object.assign can also implement deep copy, but only enumerable properties can be copied, and inherited properties cannot be copied.

function deepClone(obj) {
  return Object.assign({}, obj);
}

4. lodash implementation

lodash is a popular JavaScript tool library that provides the _.cloneDeep method for deep copying

const _ = require('lodash');
function deepClone(obj) {
  return _.cloneDeep(obj);
}