What's the regular expression that matches a square bracket? (Part II)

Question

This is a continuation of the previous thread because none of the answers there produced the intended result. I am getting super wierd behavior using regexes to match dates. I want to match the following dates:

[month-day]

Such as:

"[01-23]" // January 23rd is a valid date
"[02-31]" // February 31st is an invalid date
"[02-16]" // valid
"[ 6-03]" // invalid format

Here is my regex:

regex = /\[^[0-1][1-9]\-[0-3][0-9]\]/

I tried to put both a single \ and double \ infront of brackets but nothing seems to be working for matching these dates. Any ideas?

Thanks!

It's not going to do that. In that context, it will be treated as a literal caret. I think what you actually mean is this /^\[[0-1][1-9]\-[0-3][0-9]\]/ — rhuffstedtler, Apr 01 '15 at 12:55

score 4 · Accepted Answer · answered Apr 01 '15 at 12:55

The problem with your regex is the placement of the start-of-line anchor ^ after the initial square bracket. This cannot happen, so your regex never matches anything.

Move the anchor to the beginning of your expression to fix the problem:

regex = /^\[[0-1][1-9]\-[0-3][0-9]\]/

score 2 · Answer 2 · answered Apr 01 '15 at 12:55

2

Put the "start of line" character ^ first:

regex = /^\[[0-1][1-9]-[0-3][0-9]\]/

And you don't need to escape the middle minus - in that context.

answered Apr 01 '15 at 12:55

bloodyKnuckles

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score 1 · Answer 3 · answered Apr 01 '15 at 12:56

1

You put the anchor ^ in the wrong place. It has to be in the very front or it'll never match. Moreover, your regex doesn't even work the way you want it to work:

https://regex101.com/r/tV8hH7/1

answered Apr 01 '15 at 12:56

m0meni

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Ah alright. Best of luck to you then unless you want help with that too – m0meni Apr 01 '15 at 12:57

What's the regular expression that matches a square bracket? (Part II)

3 Answers3