A single regex for two different options

Question

How can I use the regex twice type like this:

let A =  /^A2\d{8}.{26}\d{12}$ , ^A3\d{16}.{26}\d{15}$/;

What would be the way to use it to A2 and A3 without having to use regex twice, like:

let A =  /^A2\d{8}.{26}\d{12}$/;
let A1 = /^A3\d{16}.{26}\d{15}$/;

Here an example:

A220180829Dinheiro                 1000000300767
A310180829Dinheiro                 2000000002600

Answer 1

Just one detail, one of the regex you used:

let A1 = /^A3\d{16}.{26}\d{15}$/;

Does not match the example text:

A220180829Dinheiro                 1000000300767
A310180829Dinheiro                 2000000002600

'Cause after "A3," she considers it to be 16 digits (\d{16}), but the above text only has 8. Also, at the end of the regex it looks for 15 digits (\d{15}), but the above text only has 13 (so the above regex will not give match in the second line of the text).

So I will consider two options: that the regex is correct and the text is wrong, or vice versa.

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Considering the regex and ignoring the example text

If you want a single regex that considers both options, use alternation (considering the regex that are in the question). That is, instead of having these two expressions:

let A =  /^A2\d{8}.{26}\d{12}$/;
let A1 = /^A3\d{16}.{26}\d{15}$/;

I put them together in one:

let a2OUa3 = /^(A2\d{8}.{26}\d{12}|A3\d{16}.{26}\d{15})$/;

The character | means "or". This means that the above regex considers the string may have "A2" (followed by 8 digits, etc) or "A3" (followed by 16 digits, etc).

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Considering the example text and ignoring the second regex

Now if you want to consider the text you put in the question (with 8 digits after "A3", and not 16 as it is in the regex of the question), there are other options.

In this case, at first it can be either "A2" or "A3", and the rest is equal, so an alternative is to use a character class:

let a2OUa3 = /^A[23]\d{8}.{26}\d{12}$/;

In the case, [23] means "the digit 2 or the digit 3".

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You could also use alternation:

let a2OUa3 = /^(A2|A3)\d{8}.{26}\d{12}$/;

A2|A3 means "A2 or A3" (grouped in parentheses as the | has less precedence).

Of course another option would be:

let a2OUa3 = /^A(2|3)\d{8}.{26}\d{12}$/;

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The difference is that the character class can only be used when the options match only one character. The toggle can be used for expressions of any size.

That is to say:

• (A2|A3) means "A2 or A3"
• [A2|A3] means "the letter A, or the digit 2, or the character |, or the letter A, or the digit 3" (only one of them - it is worth noting that the letter A is redundant in this case)