Function chatToNum

src/qrcode.js:1431–1436

(c)

    }

    var chatToNum = function (c) {
      if (c >= '0' && c <= '9') {
        return c.charCodeAt(0) - '0'.charCodeAt(0)
      }
      throw 'illegal char :' + c
    }

    return _this
  }