准确获取URL地址参数

http://localhost:8080/?state=app&code=021axrkH0Il7Df2bEQkH0DMjkH0axrkP

准确获取code的值

getQueryString(name) {
        let reg = new RegExp('(^|&)' + name + '=([^&]*)(&|$)', 'i');
        let r = window.location.search.substr(1).match(reg);
        if (r != null) {
          return unescape(r[2]);
        }
        return null;
      }

getQueryString('code')//021axrkH0Il7Df2bEQkH0DMjkH0axrkP

getQueryString('state')//app