Question

Why is this behavior difference between parseInt() and parseFloat()?

I have a string that contains 08 in it.

When I write this code:

alert(hfrom[0]);
alert(parseInt(hfrom[0]));
alert(parseFloat(hfrom[0]));

The following output is generated:

08
0
8

Why does parseInt and parseFloat return two different results in this case?

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).