How to write repeating Regex pattern in JavaScript

Question

How to write a regex for the following pattern in JavaScript:

1|dc35_custom|3;od;CZY;GL|2;ob;BNP;MT|4;sd;ABC;MT|5;ih;DFT;FR|6;oh;AQW;MT|7;ip;CAN;MT|8;op;CAR;MT|9;ec;SMO;GL|10;do;CZT;KU|

where

the first part 1|dc35_custom| is fixed.
the second part onwards, the pattern repeats 9 times(i.e. 3;od;CZY;GL| 2;ob;BNP;MT| and so on.

The 1st character in it ranges from 2-11 and should not repeat. For example 3 appears in the first pattern, so should not appear again.

Could you elaborate on that "and so on"? Describe the pattern in words, if you can't describe it in regex. — Colin P. Hill
– Colin P. Hill, Commented May 14, 2015 at 1:06
So you want regex pattern to filter a number out and leave everything else intact? Show an example of the end result that you want. — jojo
– jojo, Commented May 14, 2015 at 1:07
Your input string is either out of sequence or pasted wrongly: |3;od;CZY;GL|2;ob;BNP;MT| — Tim Biegeleisen
– Tim Biegeleisen, Commented May 14, 2015 at 1:08
"cannot repeat" bit cannot be done with regexp. You need to check uniqueness manually (by pulling them out with either an .exec loop, or by splitting and mapping). — Amadan
– Amadan, Commented May 14, 2015 at 1:13
@Mario: It can check that one piece is not the same as another. It can't do it in a loop. Your code below only tests that non-first pieces are not the same as first, and says nothing about them being different from each other. Example: 1|dc35_custom|3;od;CZY;GL|2;ob;BNP;MT|2;sd;ABC;MT|2;ih;DFT;FR|2;oh;AQW;MT|2;ip;CAN;MT|2;op;CAR;MT|2;ec;SMO;GL|2;do;CZT;KU| matches. — Amadan
– Amadan, Commented May 14, 2015 at 1:31

Colin P. Hill · Accepted Answer · 2015-05-14 01:26:04Z

2

I'm making a lot of assumptions with this, but here's a crack at it:

1\|dc35_custom\|(([2-9]|10|11);[a-z]{2};[A-Z]{3};[A-Z]{2}\|){9}

How it works

1\|dc35_custom\| is just literal text, escaping the vertical bar operators
([2-9]|10|11) will match any number from 2 to 11.
[a-z]{2} will match two lowercase letters
[A-Z]{3} will match three uppercase letters
[A-Z]{2} will match two uppercase letters
{9} looks for nine consecutive matches of the entire sequence enclosed in parentheses

It will not, as Amadan points out, check for uniqueness, because that's a bit beyond what regex is for.

answered May 14, 2015 at 1:26

Colin P. Hill

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Mario · Accepted Answer · 2015-05-14 01:45:14Z

0

A bit tricky, but here you go

The regex: /^1\|dc35_custom(?:\|([2-9]|1[01]);[a-z]{2};[A-Z]{1,3};[A-Z]{1,2}){9}\|$/

and the Unit tests: https://regex101.com/r/lU6sJ6/2 (hit 'Unit Tests' on the left)

I assume the following:

the first group WILL ALWAYS BE THE SAME
The first part of the pattern 3;od;CZY;GL is a number between 2-11 and NO NUMBER CAN REPEAT
The second part is lowercase letters a-z, exactly two of them
The third part is uppercase letters A-Z, between 1 and 3 ( the {1,3} thing, you can change it to {3} if it's exact)
The fourth and last part is between 1 and 2 uppercase letters A-Z

answered May 14, 2015 at 1:25

Mario

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