Is there a way I can loop this prompt to repeat itself if a word or negative number are entered?

Question

A prompt for entering a max number for a higher-lower game. I need the prompt to repeat itself if a positive number is not entered.

      var maxInput = prompt("Please choose the maximum number.");
        var numberRounded = Math.round(maxInput);
        let rules = document.getElementById("rules");
        if (numberRounded > 1) {
            message.innerHTML = (numberRounded + " is the max number!");
            rules.innerHTML = ("Guess a number between 1 and " + numberRounded + "!");
            } else if (isNaN(numberRounded)) {
            var numberRounded = prompt("Please choose a number.");
        } ```

Answer 1

You can use regular expression like so:

var userInputString="";
while(!userInputString.match(/^[1-9]+[0-9]*$/)) {
  userInputString=prompt("Enter a positive whole number");
}
var userInputPositiveWholeNumber=Number(userInputString);
console.log(userInputPositiveWholeNumber);

The loop will not exit until the user has inputted a positive whole number.

This regex has a beginning - ^, and an end $, but not middle.

The beginning, following the ^:
[1-9] = a digit between 1 and 9 (so no leading zero(s)).
+ = at least one (of the preceding range).

The end, preceding the $:
[0-9] = any digit (between 0 and 9).
* = a non-negative count of occurrences - none, once, ... infinity (of the preceding range).

Note: There is a cut-off number where larger numbers will be of d.dddd+/-ed+ format and they will lose accuracy.

---

Previous version:

The first part, [1-9]+, makes sure input starts with a digit that is not zero and not a minus sign, and no other character but a digit between 1 and 9.
The second part, [0-9]* allows for any (even zero) number of digits of any digit to follow the first.
Once the loop exits, we just cast the string to a number.