Javascript Regex Check if string has word that does not belong

Question

I have a string with times (formatted HH:MM) each on a new line. I want to create a JS function to check if there is any times that does not belong. It should simply return true or false.

Example correct string: var s = "5:45\n07:00\n13:00\n17:00";

5:45
07:00
13:00
17:00

Example incorrect string: var s = "5:45\n07:00\n55:00\n17:00";

5:45
07:00
55:00 // incorrect date here, should return false
17:00

My regex experience is little to none. Playing around on Scriptular I created this expression to detect times that do match: /^[0-2]?[0-9]\:[0-5][0-9]$/m. This however is not sufficient.

So, how can I get this to work with a string s as indicated above?

function checkIfStringConforms(s)
{
  var all_good = [some magic with regex here]
  return all_good;
}

PS: I have Googled around and checked answers on SO. My regex skill is... eh.

So is 5:45 correct? H:MM is ok?

Alex K.
– Alex K.

2015-02-11 13:35:59 +00:00
Commented Feb 11, 2015 at 13:35 — Alex K.
– Alex K., Commented Feb 11, 2015 at 13:35
^(?:[0-1]?[0-9]|2[0123]):[0-5][0-9]$

Avinash Raj
– Avinash Raj

2015-02-11 13:38:00 +00:00
Commented Feb 11, 2015 at 13:38 — Avinash Raj
– Avinash Raj, Commented Feb 11, 2015 at 13:38
@AlexK. Yes it is :)

Pangolin
– Pangolin

2015-02-11 14:58:11 +00:00
Commented Feb 11, 2015 at 14:58 — Pangolin
– Pangolin, Commented Feb 11, 2015 at 14:58

Tim Pietzcker · Accepted Answer · 2015-02-11 13:39:54Z

1

Your regex is OK, but it would also match 29:00, so it needs some improvement. Then, it's always a bit more difficult to find non-matches than it is to find matches. You could try and remove all matches from the string and then see if it's empty (except for whitespace):

result = s.replace(/^(?:2[0-3]|[01]?[0-9]):[0-5][0-9]$/mg, "");

If result is empty after that, there were no illegal times in your string.

answered Feb 11, 2015 at 13:39

Tim Pietzcker

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Pangolin Over a year ago

Thanks for also correcting my regex for checking that it is a legitimate time.

Amit Joki · Accepted Answer · 2015-02-11 13:40:44Z

1

It can be done without the use of any regex. Just split on new-line and see if every date matches your format. For that we could use Array.every

function checkIfStringConforms(s) {
    return s.split("\n").every(function(str){
        var arr = str.split(":");
        return (arr[0] < 24 && arr[0] > -1) && arr[1] < (60 && arr[1] > -1)
    });
}

answered Feb 11, 2015 at 13:40

Amit Joki

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Comments

ermouth · Accepted Answer · 2015-02-11 14:03:13Z

1

/(((2[^0-3]|[3-9].):..)|(..?:[^0-5].))(\n|$)/

Regexp returns true if your s var has at least one invalid time. Please, check it carefully before use – your question is quite broad and restrictions are not fully defined. Regex assumes that you have something like x:xx or xx:xx in each line (x is a digit) – I’m not sure this assumption covers all your data.

answered Feb 11, 2015 at 14:03

ermouth

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