RandomStringGenerateFunction

let lowerAlpha = "abcdefghijklmnopqrstuvwxyz";
let upperAlpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
let num = "0123456789";

function generateRandomString(length){
  let str = '';
  for(let i = 1; i <= length; i++){
    str += `${lowerAlpha}${upperAlpha}${num}`.charAt(Math.floor(Math.random()*`${lowerAlpha}${upperAlpha}${num}`.length));
  }
  return str;
}