Question

I tried to add two numbers in Javascript:

 var output;
 output = parseInt(a)+parseInt(b);
 alert(output);

It gives wrong output value, e.g. if a = 015, and b = 05. Why is this so?
Expected result of above example should be 20.

Answer 1

If you prefix your numbers with 0, you’re specifying them in base 8. 015 is therefore 13, and the sum is 18.

Use the second parseInt argument to force a base:

var a = '015', b = '05';
var output;
output = parseInt(a, 10) + parseInt(b, 10);
alert(output); // alerts 20