holyshit.js

var regex = /\[([^\.]*?)\.?([^\.\]]*)\]/g;
var input = "123 [VALUE] abc [234.VALUE] def [123.NONONO] xyz";

function getReplacement(firstGroup, secondGroup) {
	if (firstGroup && secondGroup == 'VALUE') {
		return Promise.resolve('XXX');
	}

	if (!firstGroup && secondGroup == 'VALUE') {
		return Promise.resolve('YYY');
	}

	return Promise.resolve('undefined'); // are you sure you meant for this to be a string?
}

const promises = input.match(regex).map(function(capture) {
	const matchPerCapture = item.match(/\[([^\.]*?)\.?([^\.\]]*)\]/); // Without global flag
	const id = matchPerCapture[1];
	const attribute = matchPerCapture[2];
	return getReplacement(id, attribute).then(res => input.replace(item, res));
});

Promise.all(promises).then(() => {
	console.log('finished replacing');
	console.log('end of file');
});