String Annotations @Schneller

string-annot.js

(function (str, notes, wrap) {
	var IDX = 0, TXT = 1,
		lines = (Array(str.length + 1)).join(' ').split('');

	notes = notes.map(function (n) { 
		return [+n.replace(/\D[\s\S]*$/, '') || 0, n.replace(/^\d+\s*/, '')];
	});
	notes.sort(function (a, b) {
		return a[IDX] === b[IDX] ? 0 : (+a[IDX] < +b[IDX] ? 1 : -1); 
	}).forEach(function (n) {
		lines[n[IDX]] = '|';
	});

	lines = lines.join('');
	return [
			(wrap ? '<pre><code>' : ''),
			str,
			lines.replace(/\|/g, '^'),
			lines,
			notes.map(function (n) {
				return lines.substr(0, n[IDX]) + '+-- ' + (n[TXT] || '');
			}).join('\n'),
			(wrap ? '</code></pre>' : '')
		].join('\n');
		
}(
	'/^[^A-Z]+\\d{1-4}$/',
	[
		'1 Beginning of string', 
		'3 Anything but a regular capital letter',
		'8 1 or more times (--> 1 or more non-caps)',
		'10 Digit (0-9)',
		'12 1-4 Times (--> 1-4 digits)',
		'16 End of string'
	]
));

/* Prints:

/^[^A-Z]+\d{1-4}$/
 ^ ^    ^ ^ ^   ^ 
 | |    | | |   | 
 | |    | | |   +-- End of string
 | |    | | +-- 1-4 Times (--> 1-4 digits)
 | |    | +-- Digit (0-9)
 | |    +-- 1 or more times (--> 1 or more non-caps)
 | +-- Anything but a regular capital letter
 +-- Beginning of string

*/