function truncateString(str, num) {
  // Clear out that junk in your trunk
  var a=str.length;
  if(a > num && num>3){
      var b=3;
    var c=a+b-num;
    return str.slice(0,-c)+"...";
  }else if(a===num){
    return str;
  }else if(a<num){
    return str;
  }else if(num<=3){
    return str.slice(0,num)+"...";
  }
  else{
    return false;
  }
  
}
truncateString("A-tisket a-tasket A green and yellow basket", 11);

function truncateString(str, num) {
  // Clear out that junk in your trunk
  if (str.length > num) {
    if (num <= 3) {
      return str.slice(0, num) + "...";
    }
    return str.slice(0, num - 3) + "...";
  }
  return str;
}
truncateString("A-tisket a-tasket A green and yellow basket", 11);