NUS Matriculation Number Checksum

Matric.js

function matric(noLetter) {
	var type = noLetter.charAt(0);
	if (type === 'U') {
		type = 1;
		var weights = [6, 11, 12, 10, 12, 0];
	} else if (type === 'A') {
		type = 2;
		var weights = [-1, -1, -1, -1, -1, -1];
	} else {
		return undefined;
	}
	
	var values = [];
	var matricInt = parseInt(noLetter.substr(1));
	for (var i = 1; i <= 6; ++i) {
		values.push(
			//Round down
			Math.floor(
				//Numeric part, divided by power of 10
				matricInt / Math.pow(10, i - 1)) %
				
				//We want the last digit
				10);
	}

	var checksum = 0;
	var letters = ['B', 'A', 'E', 'H', 'J', 'L', 'M', 'N', 'R', 'U', 'W', 'X', 'Y'];
	for (var i = 0, j = values.length; i < j; ++i) {
		checksum += values[i] * weights[i];
	}

	checksum = (checksum - 1) % letters.length;
	if (checksum < 0) {
		checksum += letters.length;
	}
	return letters[checksum];
}