使用 JSON.stringify 实现深拷贝

let jsonStr = JSON.stringify(
  {
    undefind: window.vvvv,
    null: null,
    name: 'Leo',
    site: 'https://xuebin.com',
    fun: function() {
      console.log(this.name, this.site)
    },
  },
  (key, value) => {
    return typeof value === 'function' ? '' + value : value === undefined ? 'undefined' : value
  },
  2,
)

console.log(jsonStr)

let jsonObj = JSON.parse(jsonStr, (key, value) => {
  try {
    return eval('(' + value + ')')
  } catch (e) {
    return value
  }
})

console.log(jsonObj.fun())