对象深拷贝

function deepClone(obj) {
    if (!obj || typeof obj !== 'object') {
        return obj
    }
    let result = Array.isArray(obj) ? [] : {}
    for (let key in obj) {
        if (obj.hasOwnProperty(key)) {
            if (obj[key] && typeof obj[key] === 'object') {
                result[key] = deepClone(obj[key])
            } else {
                result[key] = obj[key]
            }
        }
    }
    return result
}

调用方式为 obj.deepClone()

function deepClone() {
    if (this && typeof this !== 'object' || Object.keys(this).length !== 0) {
          return this
    }
    let toString = Object.prototype.toString
    let result = determine(this) == 'Array' ? [] : {}
    for (key in this) {
          if (this.hasOwnProperty(key)) {
              if (this[key] && determine(this[key]) == 'Object' || determine(this[key]) == 'Array') {
                  result[key] = this[key].deepClone()
              } else {
                  result[key] = this[key]
              }
          }
    }
    function determine(str) {
        return toString.call(str).split(' ')[1].split(']')[0]
    }
    return result
}

深拷贝，防止递归引用栈溢出

function deepClone(obj, hash = new Map()) {
        // obj值为null或undefind
        if (obj == null) return obj
        // 如果值不为对象就返回
        if (obj instanceof RegExp) return new RegExp(obj)
        if (obj instanceof Date) return new Date(obj)
        if (typeof obj != 'object') return obj
        if (hash.has(obj)) return hash.get(obj)
        let newObj = new obj.constructor
        hash.set(obj, newObj)
        for (let key in obj) {
            if (obj.hasOwnProperty(key)) {
                newObj[key] = deepClone(obj[key], hash)
            }
        }
        return newObj
}