docs: function maskString(srcStr, mask, start, length) {
        var str = String(srcStr), ptn = /[^\u4e00-\u9fa5]/mg, ptn_ = /[\u4e00-\u9fa5]/mg;
        if (isNum(mask)) {
          length = start, start = mask, mask = '*';
        } else if (!isStr(mask)) {
          mask = '*';
        }
        var maskStr = str.substr(start, length).replace(ptn, mask).replace(ptn_, mask + mask);
        return str.substr(0, start) + maskStr + (isUdf(length) ? '' : str.substr(start + length));
      }