Javascript from salesforce id converter to add suffix characters.

convert_sf_id.js

function convertId(id) { 
	if (id == null) return id;
	id = id.replace(/\"/g, '');
	if (id.length != 15) {
		return null;
	}
	var suffix = "";
	for (var i = 0; i < 3; i++) {
		var flags = 0;
		for (var j = 0; j < 5; j++) {
			var c = id.charAt(i * 5 + j);
			if (c >= 'A' && c <= 'Z') {
				flags += 1 << j;
			}
		}
		if (flags <= 25) {
			suffix += "ABCDEFGHIJKLMNOPQRSTUVWXYZ".charAt(flags);
		} else {
			suffix += "012345".charAt(flags-26);
		}
	}
	return id + suffix;
}