!structural-replace.js

const structuralReplace = (string, pattern, replacer) => {
	if (typeof string === 'string') {

		const acc = [];
		let m;

		let prevIndex = 0;

		while (m = pattern.exec(string)) {

			const beforeMatch = string.substring(prevIndex, pattern.lastIndex - m[0].length);
			
			if (beforeMatch.length > 0) acc.push(beforeMatch);
			acc.push(replacer(m));

			prevIndex = pattern.lastIndex;

		}

		acc.push(string.substring(prevIndex));

		return acc;
	}
	else {
		// In this can the 'string' parameter must
		// be an array of strings and other things.
		return string.map(it => structuralReplace(it, pattern, replacer));
	}
}

README.md

Structural Replace Function

The first argument of this function is a string or a list of strings (yet to parse) mixed with some already parsed objects. An example usage is the following

structuralReplace(
	'**this** is **a** test',
	/\*\*(.+?)\*\*/g,
	m => ({ style: 'bold', text: m[1] })
)

and this produces an object of the following form

[
	{ style: 'bold', text: 'this' },
	'is',
	{ style: 'bold', text: 'a' },
	'test'
]