text: /**
   * String format.
   * @authore Muzudho
   * @module js/string-format
   */
  
  const IMG_DIR = 'http://game.warabenture.com/chicken-foot/img/';
  
  var gStringFormat = {
      getTilePath: (tileNumber) => {
          "use strict";
          return IMG_DIR + tileNumber + '.png';
      },
  
      /**
       * @returns {string} string or null.
       * @example
       * ### ex.
       * 'playerNum1' ---> '1'.
       * ### ex.
       * 'mat1' ---> null.
       */
      getNumberByEntryPlayerButtonId: (id) => {
          "use strict";
          let group = /^playerNum(.+)$/.exec(id);
          if (group !== null) {
              return parseInt(group[1], 10);
          }
          return null;
      },
  
      /**
       * @returns {string} string or null.
       * @example
       * ### ex.
       * 'tile1' ---> '1'.
       * ### ex.
       * 'mat1' ---> null.
       */
      getNumberByTileId: (id) => {
          "use strict";
          let group = /^tile(.+)$/.exec(id);
          if (group !== null) {
              return parseInt(group[1], 10);
          }
          return null;
      },
  
      /**
       * @returns {string} string or null.
       * @example
       * ### ex.
       * 'move1' ---> '1'.
       * ### ex.
       * 'tail1' ---> null.
       */
      getSuffixByMoveId: (id) => {
          "use strict";
          let group = /^move(.+)$/.exec(id);
          if (group !== null) {
              return parseInt(group[1], 10);
          }
          return null;
      }
  };
  