function truncateMidlle(text, maxLength = 9, numberOfLetters = 3) {

  if(text.length >= maxLength) {

    const startPart = text.slice(0, numberOfLetters);

    const endPart = text.slice(-(text.length-numberOfLetters));

    return startPart +'...'+ endPart.slice(endPart.length-numberOfLetters, endPart.length);

  }

  return text;

}

​

console.log(truncateMidlle('abcdefghijklmn', 3, 5));

console.log(truncateMidlle('bala', 3));

console.log(truncateMidlle('Text para recuperar', 18));