What's wrong with this javascript date parsing? Why does js hate the number 8?

Question

I've got an object containing dates in the format YYYY-MM-DD.

I'm extracting the various year, month and day integers so I can send them to a different API.

Here's an example of my method, using substr()

Demo: http://jsfiddle.net/AppSynergy/tELsw/

OK, it works. OH NO! - it doesn't - not quite.. What's wrong with the 3rd element, where the "08" in 8th April decides to be 0 instead?

If I change "08" to another integer e.g. "03", it's fine. But "08" causes issues..

This one is driving me crazy -- what's wrong?

If you can spot it, you deserve ice-cream.

Try having a look at this question: http://stackoverflow.com/questions/850341/workarounds-for-javascript-parseint-octal-bug — Bogdan, Jun 25 '12 at 09:36
`08` is parsed as an octal, instead of decimal. This is why we should use the radix with parseInt()`. — David Thomas, Jun 25 '12 at 09:37
Interesting to note that IE9 is the only browser I tested that follows the [ES5.1 spec correctly](http://ecma-international.org/ecma-262/5.1/#sec-15.1.2.2) and `parseInt("08")` results in `8` — Esailija, Jun 25 '12 at 09:40

score 7 · Accepted Answer · answered Jun 25 '12 at 09:37

7

08 is considered as an (invalid) octal literal by default.

You have to explicitly specify the radix in your call to parseInt() in order for this token to be considered as a decimal (base 10) number:

$("#debug").append(parseInt(date.substr(5, 2), 10) + " / ");

answered Jun 25 '12 at 09:37

Frédéric Hamidi

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OMG.. octal default? I would **never** have thought of that! Adding the specific base of 10 solves it perfectly - thanks Frédéric and others that commented! - A – Adam Marshall Jun 25 '12 at 10:05

Blaster · Answer 2 · 2012-06-25T09:49:58.600

3

You need to use parseInt with radix/base of 10 since preceding 0 converts your number in octal notation.

parseInt(yourNum, 10);

Because of that reason, it turns out that you should ALWAYS specify base when using parseInt unless you are not working on base 10 numbers.

edited Jun 25 '12 at 09:49

answered Jun 25 '12 at 09:36

Blaster

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score 2 · Answer 3 · answered Jun 25 '12 at 09:36

If string begins with "0", javascript will think the radix is eight (octal).

You need to tell javascript to parse the string by base of 10.

$.each(testData, function(i, val) {
    // sort out the date format
    var date = val.trim();
    $('#debug').append(date+' ==><br />');
    $('#debug').append(parseInt(date.substr(0, 4), 10)+' / ');
    $('#debug').append(parseInt(date.substr(5, 2), 10)+' / ');
    $('#debug').append(parseInt(date.substr(8, 2), 10)+'<br /><br />');
});

What's wrong with this javascript date parsing? Why does js hate the number 8?

3 Answers3