CODEWITHSUNDEEP
regex
rmail2006
rmail2006

Reputation: 53

Improve Regex with Groups

Just getting into regex and I am trying to write a regex for a uk national insurance number example ab123456c.

I've currently got this which works

^[jJ]{2}[\-\s]{0,1}[0-9]{2}[\-\s]{0,1}[0-9]{2}[\-\s]{0,1}[0-9]{2}[\-\s]{0,1}[a-zA-Z]$

but I was wondering if there is a shorter version for exmaple

^[jJ]{2} [ [\-\s]{0,1}[0-9]{2} ]{3} [\-\s]{0,1}[a-zA-Z]$

So repeat the [-\s]{0,1}[0-9]{2} 3 by wrapping it in some sort of group [ * ]{3}

Upvotes: 1

Views: 65

Answers (3)

yoko
yoko

Reputation: 513

If i got you right, your insurance numbers are always two letters, 6 numbers, and a final letter, A,B,C or D? Wouldn't it be the easiest way to try sth. like that 

/\w{2}\d{6}[A-D]/

you catch 2 letters at first with \w{2} , then you get 6 numbers with \d{6} and you end with a letter from A to D by [A-D]

Or, if blanks are impontant, try this

 /\w{2}\d\d \d\d \d\d [A-D]/

I dont think that shorten it much more would be possible, since when you are trying to use (\d\d ){3} it would only repeat the same pattern three times, e.g. 23 23 23

If you really want to learn RegEx, i suggest you this tutorial, it helped me a lot in the beginning of Regular Expressions

Upvotes: 3

Casimir et Hippolyte
Casimir et Hippolyte

Reputation: 89547

A simple research for a regex tutorial in your favorite search engine (duckduckgo for sure) would give you the answer faster than asking in a forum!

So what you are looking for is a non-capturing group (?:...). You can rewrite your pattern like this:

^[jJ]{2}(?:[-\s]?[0-9]{2}){3}[-\s]?[a-zA-Z]$

or like this if you use a case insensitive flag/option:

^J{2}(?:[-\s]?[0-9]{2}){3}[-\s]?[A-Z]$

An other possible way consists to remove all that is not a letter or a digit before (and eventually to use an uppercase function). Then you only need:

^J{2}[0-9]{6}[A-Z]$

As an aside, I don't understand why you start your pattern with J for the first two letters, since many others letters are allowed according to this article: https://en.wikipedia.org/wiki/National_Insurance_number

Other thing, short and efficient are two different things in computing.

for example this pattern will be efficient too and more restrictive:

^(?!N[KT]|BG|GB|[KT]N|ZZ)[ABCEGHJ-PRSTW-Z][ABCEGHJ-NPRSTW-Z][0-9][0-9][-\s]?[0-9][0-9][-\s]?[0-9][0-9][-\s]?[A-D]$

Upvotes: 3

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626738

A shorter version:

/^j{2}(?:[-\s]?\d{2}){3}[-\s]?[a-zA-Z]$/i

See the regex online demo

Note that

Upvotes: 2

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