String returned instead of Sum - Practice If and Else Statements- Solution

let num1;
let num2;
let userNum1;
let userNum2;

alert("Let's do some math!");

num1 = prompt('Please enter a number.');
  if ( isNaN(num1) ) {
    alert('You must enter a numeric value.');
  } else {
    userNum1 = parseFloat(num1);
  }

num2 = prompt('Please enter another number.');
  if (parseInt(num2) === 0) {
    alert('You cannot divide by 0. Please try again.');
  } else if ( isNaN(num2) ) {
    alert('You must enter a numeric value.');
  } else {
    userNum2 = parseFloat(num2);
  }

let message = "<h1>Math with the numbers " + num1 + " and " + num2 + "</h1>";
  message += num1 + " + " + num2 + " = " + (num1 + num2);
  message += "<br>";
  message += num1 + " * " + num2 + " = " + (num1 * num2);
  message += "<br>";
  message += num1 + " / " + num2 + " = " + (num1 / num2);
  message += "<br>";
  message += num1 + " - " + num2 + " = " + (num1 - num2);
const message2 = "<h1>You did not enter the appropriate values, refresh and try again.</h1>";

if ( isNaN(userNum1) || isNaN(userNum2) ) {
  document.write(message2);
} else {
  document.write(message);
}

 message += num1 + " + " + num2 + " = " + (num1 + num2);