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Need regular expression for mm/dd/yyyy date possibly preceded by bullet char

I need a regular expression to test for mm/dd/yyyy dates at the beginning of lines in a form field, as in the example below:
·07/29/2019 event 3
·07/08/2019-event 2
·05/29/2019: event

Users can enter as many dates and details as they want, but I need to verify the date format.

Users may also enter only one date, as below.

07/29/2019 event

Here's what I have (that doesn't work):

var dateString = /^\d{1,2}(\-|\/|\.)\d{1,2}\1\d{4}$/

But I don't know how to test (or ignore) the bullet character. I've tried . I've tried \·

But none of my efforts find the lines below valid (though I want them to be accepted):

·07/29/2019 event 3
·07/08/2019-event 2
·05/29/2019: event

Here's the context in my javascript: else if(!dateString.test(theForm.EI16.value)) {alert("Please use mm/dd/yyyy format for all dates.");theForm.EI16.focus();return false;}

Who can help?

Kevin Cross

^·?\d{1,2}(\-|\/|\.)\d{1,2}\1\d{4}

I believe you just need to use the ? to indicate the bullet may or may not be there. For the rest, you have $ which means the date is at end of end so you have to add in that there will be other characters or just remove $.

Terry Woods

Firstly, the $ at the end of your pattern matches the end of the string. ie it will cause the pattern to only match data where the $ is the end of the string, such that strings with text after the date don't match.

Terry Woods

Ha, should have refreshed my page...

Subodh Tiwari (Neeraj)

Maybe this?

(?<=\·)\d{1,2}(\/|\-|\.)\d{1,2}\1\d{4}

GessWurker

ASKER

Unfortunately, ^·?\d{1,2}(\-|\/|\.)\d{1,2}\1\d{4} just allowed this to pass:

·07/29/2019 event 3
·07/8/2019-event 2 //<--this is a problem
·05/29/2019: event

But I need all the dates to be mm/dd/yyyy

GessWurker

ASKER

And this one -- (?<=\·)\d{1,2}(\/|\-|\.)\d{1,2}\1\d{4} -- allowed this to pass:

·07/29/2019 event 3
·7/8/2019-event 2 //<--this is a problem, I need to force 07/08/2019 with a line like this; no single digit months or days allowed
·05/29/2019: event

Terry Woods

Kevin's suggestion should work. I suggest also putting the date delimiter characters into square brackets though, like this for easier reading:

var dateString = /^·\d{1,2}([\-\/.])\d{1,2}\1\d{4}/;

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Tested here:
https://jsfiddle.net/gh6v34xn/4/

Subodh Tiwari (Neeraj)

In that case, this should force the days and months to contain 2 digits

(?<=\·)\d{2}(\/|\-|\.)\d{2}\1\d{4}

Terry Woods

For disallowing single days and months try:

var dateString = /^·\d{2}([\-\/.])\d{2}\1\d{4}/;

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wilcoxon

Subodh, the issue with your solution is that it will only be true if the date is preceeded by a bullet - the bullet is optional.

This should be a working regex forcing 2 digit dates:

var dateString = /^·?\d{2}([\-\/.])\d{2}\1\d{4}/;

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Terry Woods

If the form field value contains mulitple lines, but at least one line doesn't contain a valid date, then is the value valid?

Subodh Tiwari (Neeraj)

@wilcoxon
Yes, you are correct . That pattern will match a date only when it is preceeded by a bullet.

GessWurker

ASKER

@Terry Woods: No. If multiple lines are present, each of the lines must begin with mm/dd/yyyy (preceded by the bullet char)

GessWurker

ASKER

Folks. So far, it seems all of the suggestions only care about the first entry. The second and third entries slip by with single digit months & days. Will hope to wake up to a solution. If not, tomorrow is another day! Cheers.

leakim971

/^·?\d\d\/\d\d\/\d{4}/

Subodh Tiwari (Neeraj)

So far, it seems all of the suggestions only care about the first entry. The second and third entries slip by with single digit months & days.

That shouldn't be the case if you are properly testing the string using the regex.test after setting the global flag

wilcoxon

If dateString contains all of the dates at once, you are correct - none of the solutions presented will check all of them.

This should match based on all of your criteria - 2 or more dates preceeded by bullet or 1 date without bullet, optional extra text after date, and month/day exactly 2 digits each.

var dateString = /\A(?:^·\d{2}([\-\/.])\d{2}\1\d{4}.*\n?){2,}\Z|\A\d{2}([\-\/.])\d{2}\1\d{4}.*\n?\Z/m;

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ASKER CERTIFIED SOLUTION

Terry Woods

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Terry Woods

To be honest though, it may have been sensible just to split the string by lines, then validate each line... complex regex patterns can become a headache.

GessWurker

ASKER

Folks - We've got a winner! I tested every regx you came up with and only one worked under all the circumstances/scenarios I threw at it. Terry Woods did the work. Thanks, Terry!

Kudos to Terry for the regx below:

var dateString = /^(?:·?\d{2}([\-\/.])\d{2}\1\d{4}[^\n]*(?:\n+|$))+$/;

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GessWurker

ASKER

@Terry: Regarding splitting and evaluating lines one by one... I had the same notion this morning. But then, when I couldn't break your last suggestion, I put the notion away. : )