Javascript regex to extract year from string

Question

I'm trying to extract the year from a timestamp using regex, but I'm not very good at it, so my code isn't returning what expected.

that's the string: 'Sun Jan 01 2012 00:00:00 GMT+0000 (GMT)'

I need to extract '2012' here's my code:

var scrollDate = tl.getBand(0).getCenterVisibleDate(); // my timestamp

// regex function
function extractNumbers(str) {
     var m = /(^|\s)(\d{4})(\s|$)/.exec(str);
     return m;
}

// click event
$('.n-left').click(function(){
     alert(extractNumbers(scrollDate));
});

The alert box returns this: 2012 , ,2012,

What am I doing wrong? Thanks in advance

Don't use a regex for this, it's the wrong tool for the job, use James Kleeh's approach of just letting Date parse the string. — CaffGeek
– CaffGeek, Commented Sep 7, 2012 at 16:16

James Kleeh · Accepted Answer · 2012-09-07 16:12:27Z

7

var x = new Date("Sun Jan 01 2012 00:00:00 GMT+0000 (GMT)");

 alert(x.getUTCFullYear());

answered Sep 7, 2012 at 16:12

James Kleeh

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Community · Accepted Answer · 2017-05-23 10:27:45Z

3

That regular expression uses capture groups. If you look at the return value of exec(), you’ll notice it looks something like this:

[" 2012 ", " ", "2012", " "]

So, you might want to write extractNumbers() something like this:

function extractNumbers(str) {
     var m = /(^|\s)(\d{4})(\s|$)/.exec(str);
    if (m) {
        return m[2];
    }
}

FWIW, you can use non-capturing groups to group parts of the regexp but only capture what you need. A regexp like this:

/(?:^|\s)(\d{4})(?:\s|$)/

Would return a match array like this:

[" 2012 ", "2012"]

EDIT: …but James Kleeh’s answer is like a much nicer option.

edited May 23, 2017 at 10:27

CommunityBot

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answered Sep 7, 2012 at 16:09

s4y

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Comments

Poni · Accepted Answer · 2012-09-07 16:11:56Z

0

First, it works with RegexBuddy (it returns group #1 successfully).

Another regex you might wanna try, which looks simpler to me: .+?\d\d (\d+) (then take group #1)

answered Sep 7, 2012 at 16:11

Poni

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