Question

Possible Duplicate:
Workarounds for JavaScript parseInt octal bug

Why does

parseInt("09") 

return 0 but

parseInt("07") 

return 7?

Answer 1

The base for strings starting with 0 can be octal (when a radix is not specified – and depending on the browser).

You are looking for:

parseInt("09", 10)

See the documentation for parseInt:

If radix is undefined or 0, JavaScript assumes the following:

• If the input string begins with "0x" or "0X", radix is 16 (hexadecimal).
• If the input string begins with "0", radix is eight (octal). This feature is non-standard, and some implementations deliberately do not support it (instead using the radix 10). For this reason always specify a radix when using parseInt.
• If the input string begins with any other value, the radix is 10 (decimal).

The comments for the radix optional parameter (the second one in my example) says this:

While this parameter is optional, always specify it to eliminate reader confusion and to guarantee predictable behavior.