Question

My code looks like follows

var html = $(el).html().toString();
html = '2012-05-10';
var re = new RegExp('^(19|20)\d\d[- /.](0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])$');
var m = re.exec(html);
if (m != null)
alert('match');
else
alert('nomatch');

The purpose of the regexp is to check whether a string contains any dates. However it never finds any dates. I have tested the regexp with an online regexp tool.

Answer 1

If you’re trying to find whether a string contains any dates, then having ^ at the start and $ isn’t going to help – as they denote to match the very start and end of the string.

To find the date within a string that contains other text (or even whitespace), use this…

var re = new RegExp('(19|20)\d\d[- /.](0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])');

UPDATE

Anton has already figured out a solution – however, while the above solution is better than the original, it’s still not correct, as the \d needs to be escaped (to \\d) in order for it to work when contained within quotes. So instead it should be…

var re = new RegExp('(19|20)\\d\\d[- /.](0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])');

However, in hindsight I agree with all others that as it’s not a dynamic pattern, the best solution is to use the /pattern/ syntax