toTXT(str) {
       var RexStr = /\<|\>|\"|\'|\&|　| /g
       str = str.replace(RexStr,
          function(MatchStr) {
             switch(MatchStr) {
                case "<":
                   return "<";
                   break;
                case ">":
                   return ">";
                   break;
                case "\"":
                   return """;
                   break;
                case "'":
                   return "'";
                   break;
                case "&":
                   return "&";
                   break;
                case " ":
                   return " ";
                   break;
                case "　":
                   return " ";
                   break;
                default:
                   break;
             }
          }
       )
       return str;
    }