randomId.js

function randomId(lenght) {
	var charSet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_';
	var id = '';
	var randPos = 0;

	for (var i = 1; i <= lenght; i++) {
		randPos = Math.floor(Math.random() * charSet.length);
		id += charSet[randPos];
	}

	return id;
}