My solution w/ while loop used to keep asking the user for a valid input

// Collect input from a user
let randLow = prompt("Input a number and we will provide a random number between this number and another number");
let randHigh = prompt(`Input a number and we will provide a random number between ${randLow} and this number`);


// Check if user inputs are integers
if(isNaN(+randLow) || isNaN(+randHigh)){ 

  /*
    while loop to check if any of the inputs are invalid
    isNaN method checks if a variable is NaN
    If either one is not an integer, it will keep on asking the user for one.
  */
  while(isNaN(+randLow) || isNaN(+randHigh)){

    // if low input is not an integer
    if(isNaN(+randLow)) {
      document.querySelector('main').innerHTML = `<h2>${randLow} is not a number, try again.</h2>`;
      randLow = prompt("Input a number and we will provide a random number between this number and another number");
    }

    // if high input is not an integer
    if(isNaN(+randHigh)) {
      document.querySelector('main').innerHTML = `<h2>${randHigh} is not a number, try again.</h2>`;
      randHigh = prompt(`Input a number and we will provide a random number between ${randLow} and this number`);
    }
  }

  // if both are now integers
  if(!(isNaN(+randLow) || isNaN(+randHigh))) {
    // Use Math.random() and the user's numbers to generate a random number
    let randNum = Math.floor(Math.random() * (+randHigh - +randLow + 1)) + +randLow

    // Create a message displaying the random number
    document.querySelector('main').innerHTML = `<h2>${randNum} is a number between ${randLow} & ${randHigh}!</h2>`;
  }

} else { // if both are right out of the bat
    // Use Math.random() and the user's number to generate a random number
    let randNum = Math.floor(Math.random() * (+randHigh - +randLow + 1)) + +randLow

    // Create a message displaying the random number
    document.querySelector('main').innerHTML = `<h2>${randNum} is a number between ${randLow} & ${randHigh}!</h2>`;
}