判断数据类型

    function getType(target) {
      // 先处理最特殊的null
      if (target === null) {
        return "null";
      }
      // 判断是否为基本数据类型
      let type = typeof target;
      if (type !== 'object') {
        return type;
      }
      // 为引用数据类型
      const template = {
        "[object Object]": "object",
        "[object Array]": "array",
        "[object Function]": "function",
        // 为包装类型
        "[object String]": "object-string",
        "[object Number]": "object-number",
        "[object Boolean]": "object-boolean"
      }
      const typeStr = Object.prototype.toString.call(target);
      return template[typeStr];
    }