Multiple nested matches in JavaScript Regular Expression

Question

Trying to write a regular expression to match GS1 barcode patterns ( https://en.wikipedia.org/wiki/GS1-128 ), that contain 2 or more of these patterns that have an identifier followed by a certain number of characters of data.

I need something that matches this barcode because it contains 2 of the identifier and data patterns:

human readable with the identifiers in parens: (01)12345678901234(17)501200

actual data: 011234567890123417501200

but should match not this barcode when there is only one pattern in:

human readable: (01)12345678901234

actual data: 0112345678901234

It seems like the following should work:

var regex = /(?:01(\d{14})|10([^\x1D]{6,20})|11(\d{6})|17(\d{6})){2,}/g;
var str = "011234567890123417501200";

console.log(str.replace(regex, "$4"));
// matches 501200
console.log(str.replace(regex, "$1"));
// no match? why?

For some strange reason as soon as I remove the {2,} it works, but I need the {2,} so that it only returns matches if there is more than one match.

// Remove {2,} and it will return the first match
var regex = /(?:01(\d{14})|10([^\x1D]{6,20})|11(\d{6})|17(\d{6}))/g;
var str = "011234567890123417501200";

console.log(str.replace(regex, "$4"));
// matches 501200
console.log(str.replace(regex, "$1"));
// matches 12345678901234
// but then the problem is it would also match single identifiers such as
var str2 = "0112345678901234";
console.log(str2.replace(regex, "$1"));
 

How do I make this work so it will only match and pull the data if there is more than 1 set of match groups?

Thanks!

Answer 1

Your RegEx is logically and syntatically correct for Perl-Compatible Regular Expressions (PCRE). The issue I believe you are facing is the fact that JavaScript has issues with repeated capture groups. This is why the RegEx works fine once you take out the {2,}. By adding the quantifier, JavaScript will be sure to return only the last match.

What I would recommend is removing the {2,} quantifier and then programmatically checking for matches. I know it's not ideal for those who are big fans of RegEx, but c'est la vie.

Please see the snippet below:

var regex = /(?:01(\d{14})|10([^\x1D]{6,20})|11(\d{6})|17(\d{6}))/g;
var str = "011234567890123417501200";

// Check to see if we have at least 2 matches.
var m = str.match(regex);
console.log("Matches list: " + JSON.stringify(m));
if (m.length < 2) {
    console.log("We only received " + m.length + " matches.");
} else {
    console.log("We received " + m.length + " matches.");
    console.log("We have achieved the minimum!");
}

// If we exec the regex, what would we get?
console.log("** Method 1 **");
var n;
while (n = regex.exec(str)) {
    console.log(JSON.stringify(n));
}

// That's not going to work.  Let's try using a second regex.
console.log("** Method 2 **");
var regex2 = /^(\d{2})(\d{6,})$/;
var arr = [];
var obj = {};
for (var i = 0, len = m.length; i < len; i++) {
    arr = m[i].match(regex2);
    obj[arr[1]] = arr[2];
}

console.log(JSON.stringify(obj));

// EOF

I hope this helps.