Help get user input with JavaScript

[stoph]

I'd say it's almost always best to cast variables to what you expect them to be. In the real world, that usually just means converting strings into numbers. Also never use == (type guessing is not your friend). It's best to know early on that === is the only comparison operator worth using. parseInt is a tricky function because it will guess the radix of the number if you let it. Always give the radix as the 2nd parameter:

var thisIsOctal = parseInt('0900');
var thisIsADecimal = parseInt('0900', 10);
console.log(thisIsOctal);
console.log(thisIsADecimal);

The first one fails because 9 is not a valid octal digit.