Want user to input number for for loop to run Javascript

Question

Trying to have a user input a number and if they type in a string I would like to prompt them to enter a number. Seems like I got that part right but how can I get the second prompt to keep popping up until the user enters a an actual number. As of now, once the user enters a string again nothing runs after that. Would appreciate any kind of suggestions.

Here is the code:

function enterNumber(n) {

    n = parseInt(prompt("Please enter a number: "));

    if (isNaN(n)) {
        n = parseInt(prompt("You did not enter a number. Please enter a number: "));

            for(var i = 1; i <= n; i++) {

            if (i % 15 === 0) {
                document.write("Fizz Buzz" + "<br>");
                continue;
            }
            else if (i % 3 === 0){
                document.write("Fizz" + "<br>");
                continue;
            } else if (i % 5 === 0) {
                document.write("Buzz" + "<br>");
                continue;
            }
            document.write(i + "<br>");
        }
    }

};
enterNumber();

Give them a input field, and only run the function which has the loop if the input is a number. — Swaraj Giri
– Swaraj Giri, Commented Sep 24, 2015 at 5:04

Tushar · Accepted Answer · 2015-09-24 05:15:05Z

2

Use while loop until the entered is number.

function enterNumber(n) {
  while (isNaN(parseInt(n))) {
    n = parseInt(prompt("Please enter a number: "));
  }

  for (var i = 1; i <= n; i++) {

    if (i % 15 === 0) {
      document.write("Fizz Buzz" + "<br>");
      continue;
    } else if (i % 3 === 0) {
      document.write("Fizz" + "<br>");
      continue;
    } else if (i % 5 === 0) {
      document.write("Buzz" + "<br>");
      continue;
    }
    document.write(i + "<br>");
  }

};

enterNumber();

You can also shorten you code using nested Ternary operators as follow.

function enterNumber(n) {
  while (isNaN(parseInt(n))) {
    n = parseInt(prompt("Please enter a number: "));
  }

  for (var i = 1; i <= n; i++) {
    var title = i % 15 === 0 ? 'Fizz Buzz' : i % 3 === 0 ? 'Fizz' : i % 5 === 0 ? 'Buzz' : i;
    document.write(title + "<br>");
  }
};

enterNumber();

edited Sep 24, 2015 at 5:15

answered Sep 24, 2015 at 5:06

Tushar

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1 Comment

David Trinh Over a year ago

Oh thats even better I am gonna read up on that...looks like it will make life a lot easier

Tushar · Accepted Answer · 2015-09-24 05:17:58Z

1

Try like this

function enterNumber(n) {


  while (isNaN(n))
    n = parseInt(prompt("You did not enter a number. Please enter a number: "));


  for (var i = 1; i <= n; i++) {

    if (i % 15 === 0) {
      document.write("Fizz Buzz" + "<br>");
      continue;
    } else if (i % 3 === 0) {
      document.write("Fizz" + "<br>");
      continue;
    } else if (i % 5 === 0) {
      document.write("Buzz" + "<br>");
      continue;
    }
    document.write(i + "<br>");
  }


};
enterNumber();

edited Sep 24, 2015 at 5:17

Tushar

87.4k21 gold badges164 silver badges182 bronze badges

answered Sep 24, 2015 at 5:08

Man Programmer

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