const regex = /^ # Assert begin of line
(?= # First zero-with lookahead
( # Capturing group 1
a # Match a
(?1)? # Recurse group 1 optionally
b # Match b
) # End of group 1
c+ # Match c one or more times
) # End of the first lookahead
(?= # Second zero-with lookahead
a+ # Match a one or more times
( # Capturing group 2
b # Match b
(?2)? # Recurse group 2 optionally
c # Match c
) # End of group 2
) # End of the second lookahead
a+b+c+ # Match each of a,b and c one or more times
$ # Assert end of line/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('^ # Assert begin of line
(?= # First zero-with lookahead
( # Capturing group 1
a # Match a
(?1)? # Recurse group 1 optionally
b # Match b
) # End of group 1
c+ # Match c one or more times
) # End of the first lookahead
(?= # Second zero-with lookahead
a+ # Match a one or more times
( # Capturing group 2
b # Match b
(?2)? # Recurse group 2 optionally
c # Match c
) # End of group 2
) # End of the second lookahead
a+b+c+ # Match each of a,b and c one or more times
$ # Assert end of line', 'gm')
const str = `abc
aabbcc
aaabbbccc
abbc
aabbc
aabbbccc
ab
aabb
aaabbb`;
// Reset `lastIndex` if this regex is defined globally
// regex.lastIndex = 0;
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}`);
});
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions