freecodecamp challenge: Truncate String function

truncateString

function truncateString(str, num) {
    if (str.length <= num) {
        console.log(str);
        return str;
    } else {
        

     var newStr = [];
     var nstr = str.split("");
   for (let index = 0; index < num; index++) {
        newStr.push(nstr[index])
     
   }   
   str =  newStr.join('') + '...'; 
   console.log(str);
   return str;
  }
}
  truncateString("A-tisket a-tasket A green and yellow basket", 8) ;
truncateString("Peter Piper picked a peck of pickled peppers", 11) ;
truncateString("A-tisket a-tasket A green and yellow basket", "A-tisket a-tasket A green and yellow basket".length) ;
truncateString("A-tisket a-tasket A green and yellow basket", "A-tisket a-tasket A green and yellow basket".length + 2) ;
truncateString("A-", 1);
truncateString("Absolutely Longer", 2) ;

/*
* credits Kaeyz (Kolade)
// permission to reuse
! link https://github.com/Kaeyz
? FreeCodeCamp Ibadan

*/
// TODO write the code below
function truncateString(str, num) {
  let store = []
  let strArray = str.split('');
  if (str.length <= num) {
    return str
  } else {
    for (let index = 0; index < num; index++) {
      store.push(strArray[index])
    }
    // str = output.join('') + '...';
    return store.join('').concat('...')
  }
}

truncateString("A-tisket a-tasket A green and yellow basket", 8)