Always pass the radix to parseInt

The parseInt method takes two parameters:
parseInt(value, radix);
The second parameter specifies the current numeral system. In the case it's not specified, then it will be set automatically based on the value. If the value starts with 0x or 0X, then the radix is 16 (hexadecimal). In other cases, the radix is 10 (decimal).
In the older versions of JavaScript, if the string starts with 0 then the radix is set as 8 (octal).
parseInt('0xF'); // 15
parseInt('0XF'); // 15
parseInt('0xF', 16); // 15
parseInt('0xF', 10); // 0
Since the method could be implemented differently in different versions of JavaScript and browsers, it's recommended to pass the radix number.