truncate javascript

const string = "Name".slice(0, 250).concat('...');
const string2 = "Name".substring(0, 250).concat('...');function truncateString(str, num) {
  if (num > str.length){
    return str;
  } else{
    str = str.substring(0,num);
    return str+"...";
  }

}

res = truncateString("A-tisket a-tasket A green and yellow basket", 11);
alert(res)var string = "ABCDEFG";
var truncString = string.substring(0, 3); //Only keep the first 3 characters
console.log(truncString); //output: "ABC"