Javascript adding numbers

[LessThanSatisfactory]

var num1 = prompt("What is number 1?");var num2 = prompt("What is number 2?");var num3 = num1 + num2;{    alert("The answer is " + num3);}

A bit of my code goes a little like this, but instead of mathematically adding the two numbers, it shows (number1)(number2), for example, if I try to add 1 and 2, I get 12.

[Nuluvius]

This is because you are concatenating strings. You need to cast your inputs to numbers first and then add them:

var num1 = Number(prompt("What is number 1?"));var num2 = Number(prompt("What is number 2?"));var num3 = num1 + num2;alert("The answer is " + num3);

Made you a fiddle: http://jsfiddle.net/3qvPt/

 

There's also parse functions such as parseInt & parseFloat.