验证字符长度

strlen(str) {
      var len = 0;
      for (var i = 0; i < str.length; i++) {
        var c = str.charCodeAt(i);
        //单字节加1
        if ((c >= 0x0001 && c <= 0x007e) || (0xff60 <= c && c <= 0xff9f)) {
          len++;
        } else {
          len += 2;
        }
      }
      return len;
    },