function randomIntFromInterval(min, max) { // min and max included 
  return Math.floor(Math.random() * (max - min + 1) + min);
}

const rndInt = randomIntFromInterval(1, 6);
console.log(rndInt);

What it does "extra" is it allows random intervals that do not start with 1. So you can get a random number from 10 to 15 for example. Flexibility.

you need to get a new number and compare with the old one, if it's the same one, get a new one and repeat. a little recursuion could help here!

let lastNumber // start with undefined lastNumber

function getRandNumber() {
  var x = Math.floor((Math.random() * 5) + 1); // get new random number

  if (x === lastNumber) { // compare with last number
    return getRandNumber() // if they are the same, call the function again to repeat the process
  }
  return x // if they're not the same, return it
}
function myFunction() {
   const number = getRandNumber()
   lastNumber = number 
   document.getElementById("demo").innerHTML = number;
}