Checks ABA routing number checksum

gistfile1.js

/**
 * function to test if a given value (string/int) passes a basic ABA routing number checksum
 */
function isValidABA(aba) {
	var numericRegex = /^\d{9}$/,
		total = null;

	// just in cases
	aba = aba.toString();

	// make sure it's numeric and of length 9
	if ( !numericRegex.test( aba ) ) {
		return false;
	}

	// compute checksum
	for (var i=0; i<9; i += 3) {
		total += parseInt(aba.charAt(i), 10) * 3
			+ parseInt(aba.charAt(i + 1), 10) * 7
			+ parseInt(aba.charAt(i + 2), 10);
	}
	if (total !== 0 && total % 10 === 0){
		return true;
	}

	// still here? That's not good.
	return false;
}