Behavior difference between parseInt() and parseFloat() [duplicate]

Answer 1

parseInt() assumes the base of your number according to the first characters in the string. If it begins with 0x it assumes base 16 (hexadecimal). Otherwise, if it begins with 0 it assumes base 8 (octal). Otherwise it assumes base 10.

You can specify the base as a second argument:

alert(parseInt(hfrom[0], 10)); // 8

From MDN (linked above):

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).

Answer 2

you should always include the radix param with parseInt() ex parseInt('013', 10) otherwise it can convert it to a different numeric base:

parseInt('013') === 11
parseInt('013', 10) === 13
parseInt('0x13') === 19