const regex = /(\(([^(){},]+|\((?:[^(),]+,[^(),]+)\)|({(?:[^{}]+|(?-1))++}))(?:,(?2))+),/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('(\\(([^(){},]+|\\((?:[^(),]+,[^(),]+)\\)|({(?:[^{}]+|(?-1))++}))(?:,(?2))+),', 'gm')
const str = `Should work for:
(1,2,3)
(1,2,3,4)
((1,2),3,4)
(((1,2,3),4),5)
({x},{y},{z})
(1,(2,3),4)
((1,2),(3,4),5)
((1,2),3,(4,5))
(1,(2,(3,4),5))
(1,(2,({3},4),5))
(1,{{1},{1,2}},3)
Should not work for:
(1,2)
(10,10)
(1,10)
((1,2),3)
(((1,1),1),1)
({0},1)
({{x},{x,y}},z)`;
const subst = `($1),`;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
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