Question

I need to extract the last date only from a string that looks like the following:

Week 1: 03/06/11 – 03/13/11\n

What regex can I use to get ’03/13/11′?

Answer 1

You can use a regular expression to match both the first and second date and then reference just the second match:

var str = "Week 1: 03/06/11 - 03/13/11\n";
var secondDate;
var matches = str.match(/(\d+\/\d+\/\d+)\s*-\s*(\d+\/\d+\/\d+)/);
if (matches) {
    secondDate = matches[2];
}

In answer to your other question, the specific regex to match ’03/13/11′ is:

/\d+\/\d+\/\d+/

which means:

one or more digits 
followed by a / 
followed by one or more digits 
followed by a slash 
followed by one or more digits.

The advantage of using a regex here is that you can more easily build in flexibility for variable spacing, characters in the string after the second date, etc… For example, this regex works with all of these:

Week 1: 03/06/11 - 03/13/11\n
Week 1: 3/06/11 - 3/13/11\n
Week 1: 3/06/2011 - 3/13/2011\n
Week 1: 3/6/11 - 3/13/11\n
Week 1: 03/06/11 - 03/13/11
Week 1: 03/06/11-03/13/11\n
Week - 1: 03/06/11 - 03/13/11\n
Week 1: 03/06/11 - 03/13/11 and Week 2: 03/014/11 - 03/18/11

In addition matches[1] is also the first date so you get both dates with the regex too if that’s helpful.

The other methods provided using split or indexOf do not necessarily have the flexibility to automatically work with all these varying formats.