Mikael's blog

A developers seventh time trying to maintain a blog

A Tiny Bug

I’ve been using (and still am in production) an old JavaScript function called parseInt when parsing my DateTimes for comments and posts. For some reason it showed some weird behavior today.

I noticed a comment that was written on December 0. I looked it up in the database and it turns out it was actually written on December 8. Now the 8 should have been parsed from the DateTime 2011-11-08 ... into the string "08" and then I assumed parseInt should have gotten rid of that extra 0 for me.

I found my problem in the parseInt documentation over at w3schools.

The parseInt() function parses a string and returns an integer.

The radix parameter is used to specify which numeral system to be used, for example, a radix of 16 (hexadecimal) indicates that the number in the string should be parsed from a hexadecimal number to a decimal number.

If the radix parameter is omitted, JavaScript assumes the following:

If the string begins with “0x”, the radix is 16 (hexadecimal)
If the string begins with “0”, the radix is 8 (octal). This feature is deprecated
If the string begins with any other value, the radix is 10 (decimal)

parseInt works fine for the strings “01” through “07” and of course for any string beginning with a “1”. The deprecated “string begins with a zero”-feature was the culprit.

So today I learned something new; use Number() instead.

by Mikael Lofjärd
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