index.js

const SmsCounter = () => {};

SmsCounter.gsm7bitChars =
  '@£$¥èéùìòÇ\\nØø\\rÅåΔ_ΦΓΛΩΠΨΣΘΞÆæßÉ !\\"#¤%&\'()*+,-./0123456789:;<=>?¡ABCDEFGHIJKLMNOPQRSTUVWXYZÄÖÑܧ¿abcdefghijklmnopqrstuvwxyzäöñüà';

SmsCounter.gsm7bitExChar = '\\^{}\\\\\\[~\\]|€';

SmsCounter.gsm7bitRegExp = RegExp('^[' + SmsCounter.gsm7bitChars + ']*$');

SmsCounter.gsm7bitExRegExp = RegExp('^[' + SmsCounter.gsm7bitChars + SmsCounter.gsm7bitExChar + ']*$');

SmsCounter.gsm7bitExOnlyRegExp = RegExp('^[\\' + SmsCounter.gsm7bitExChar + ']*$');

SmsCounter.GSM_7BIT = 'GSM_7BIT';

SmsCounter.GSM_7BIT_EX = 'GSM_7BIT_EX';

SmsCounter.UTF16 = 'UTF16';

SmsCounter.messageLength = {
  GSM_7BIT: 160,
  GSM_7BIT_EX: 160,
  UTF16: 70,
};

SmsCounter.multiMessageLength = {
  GSM_7BIT: 153,
  GSM_7BIT_EX: 153,
  UTF16: 67,
};

SmsCounter.count = text => {
  let encoding, length, messages, per_message, remaining;
  encoding = SmsCounter.detectEncoding(text);
  length = text.length;

  if (encoding === SmsCounter.GSM_7BIT_EX) {
    length += SmsCounter.countGsm7bitEx(text);
  }

  per_message = SmsCounter.messageLength[encoding];

  if (length > per_message) {
    per_message = SmsCounter.multiMessageLength[encoding];
  }

  messages = Math.ceil(length / per_message);

  remaining = per_message * messages - length;

  if (remaining === 0 && messages === 0) {
    remaining = per_message;
  }

  return {
    encoding: encoding,
    length: length,
    per_message: per_message,
    remaining: remaining,
    messages: messages,
  };
};

SmsCounter.detectEncoding = text => {
  switch (false) {
    case text.match(SmsCounter.gsm7bitRegExp) == null:
      return SmsCounter.GSM_7BIT;
    case text.match(SmsCounter.gsm7bitExRegExp) == null:
      return SmsCounter.GSM_7BIT_EX;
    default:
      return SmsCounter.UTF16;
  }
};

SmsCounter.countGsm7bitEx = text => {
  let char2, chars;

  chars = () => {
    let _i, _len, _results;
    _results = [];
    for (_i = 0, _len = text.length; _i < _len; _i++) {
      char2 = text[_i];

      if (char2.match(SmsCounter.gsm7bitExOnlyRegExp) != null) {
        _results.push(char2);
      }
    }
    return _results;
  };

  return chars.length;
};

module.exports = SmsCounter;