RegEx for matching 3 alphabets and 1-2 digits - regex

Question

I am trying to write a regular expression to find a match in a text having at least 100 characters. The match should be like this - Any sub string within a string that contains at least 3 alphabet to begin with, at least 1 digit following it and a maximum of 2 digits following the 3 letters.
Examples -
abcjkhklfdpdn24hjkk - In this case I want to extract pdn24
hjdksfkpdf1lkjk - In this case I want to extract pdf1
hjgjdkspdg34kjfs dhj khk678jkfhlds1 - In this case I want both pdg34 and lds1
How do I write a regex for this ? The length of the starting letters for a match is always 3 and the digits length can be either 1 or 2 (not more not less)
This is what works if there are 2 digits after the 3 letter string.
[A-Za-z]{3}[0-9]{2}
But the length of the digits can vary between 1 and 2. How do I include the varying length in the regex?

Answer 1

The expression we wish to design is quite interesting. We can first add your original expression with a slight modification in a capturing group, then we should think of left and right boundaries around it. For instance, on the right we might want to use \D:
([A-Za-z]{3}[0-9]{1,2})\D
DEMO 1
We can surely define an exact restricted expression. However, this might just work.
Based on Cary Swoveland's advice, we can also use this expression, which is much better:
\p{L}{3}\d{1,2}(?!\d)
Test
re = /([A-Za-z]{3}[0-9]{1,2})\D/m
str = 'abcjkhklfdpdn24hjkk
hjdksfkpdf1lkjk
hjgjdkspdg34kjfs dhj khk678jkfhlds1 '
# Print the match result
str.scan(re) do |match|
puts match.to_s
end
This script shows how the capturing group works:
const regex = /([A-Za-z]{3}[0-9]{1,2})\D/gm;
const str = `abcjkhklfdpdn24hjkk
hjdksfkpdf1lkjk
hjgjdkspdg34kjfs dhj khk678jkfhlds1 `;
let m;
while ((m = regex.exec(str)) !== null) {
// This is necessary to avoid infinite loops with zero-width matches
if (m.index === regex.lastIndex) {
regex.lastIndex++;
}
// The result can be accessed through the `m`-variable.
m.forEach((match, groupIndex) => {
console.log(`Found match, group ${groupIndex}: ${match}`);
});
}

Answer 2

At least 3 alphabets: [a-zA-Z]{3,}
1 or 2 digits (not more not less): [0-9]{1,2}
This gives us:
/[a-zA-Z]{3,}[0-9]{1,2}/