Optimized JavaScript string trim

gistfile1.js

function trim(str)
{
	// immediate return!
	if(!str)return '';

	// markers
	var modified = false, start = -1, end = str.length;

	// traverse from beginning and from end for markers...
	while(str.charCodeAt(--end) < 33 || str.charCodeAt(end) == 65279) modified = true;
	while(str.charCodeAt(++start) < 33 || str.charCodeAt(start) == 65279) modified = true;

	// return slice only if modified
	return modified ? str.slice(start, end + 1) : str;
}