Question

I have numbers in javascript from 01(int) to 09(int) and I want add 1(int) to each one.

For example:

01 + 1 = 2
02 + 1 = 3

But

08 + 1 = 1
09 + 1 = 1

I know the solution. I’ve defined them as float type.

But I want to learn, what is the reason for this result?

Thank you.

Answer 1

Javascript, like other languages, may treat numbers beginning with 0 as octal. That means only the digits 0 through 7 would be valid.

What seems to be happening is that 08 and 09 are being treated as octal but, because they have invalid characters, those characters are being silently ignored. So what you’re actually calculating is 0 + 1.

Alternatively, it may be that the entire 08 is being ignored and having 0 substituted for it.

The best way would be to try 028 + 1 and see if you get 3 or 1 (or possibly even 30 if the interpretation is really weird).