JSFiddle - React, Tailwind, and code Playground

JavaScript

var s = 'how((\\s+can|\\s+do)(\\s+i)?)?';
var token = "\u1234";
var patt1 = /([^\\])(?=\()/g;
var patt2 = new RegExp(token + '\\(', 'g');

s = s.replace(patt1, "$1" + token).replace(patt2, "(?:");

console.log(s);