adding variables (from strings to numbers)

[EfremJ]

I know I'm probably missing something really simple but I cannot for the life of me get this code to work:

// variables section
var firstNumber;
var secondNumber;
var outputNumber;

// input section
firstNumber = prompt("Enter a number:");
secondNumber = prompt("Enter a second number:");

// processing section
outputSum = firstNumber + secondNumber;

//output section
document.write(outputNumber);

When I am prompted to input a number, I type in 15. When I am prompted for the second number I type 10.

I want them to add up to 25 but they keep adding as strings and producing "1510".

What am I missing..?

[Fotiman]

Welcome to WebmasterWorld! In JavaScript, the + operator also acts as the string concatenation operator. What you need to do is force your variables to be interpreted as numbers. One way you could do this is using the parseInt and parseFloat functions. For example:

outputSum = parseInt(firstNumber, 10) + parseInt(secondNumber, 10);

Hope that helps. :)

[EfremJ]

Hi, Fotiman.

I'll give that a try and see how it works. Thanks for the response!

[EfremJ]

That worked like a charm! Thanks so much for the assistance!

[rocknbil]

For posterity's sake, it sometimes gets worse when you try to add decimal numbers [webmasterworld.com].

[EfremJ]

rocknbil--thanks for the reference. I'll definitely make a note of it for posterity. For the present, the challenge is based on whole numbers, so that's a bit of a relief for me!