Validate New Zealand NHI Number

ValidateNZNHI

// Description: Returns true if a New Zealand NHI passes checksum validation, otherwise returns false.
function is_nz_nhi(NHI) {
    var passTest = false;
    // Validation steps 1 and 2
    if (/^[A-HJ-NP-Z]{3}[0-9]{4}$/.test(NHI)) {
        var checkValue = 0;
        // Init alpha conversion table omitting O and I. A=1~Z=24
        var aplhaTable = "ABCDEFGHJKLMNPQRSTUVWXYZ".split('');
        for (i = 0; i < 3; i++) {
            // Convert each letter to numeric value from table above
            var letterNumeric = aplhaTable.indexOf(NHI[i]) + 1
            // Multiply numeric value by 7-i and add to the checkvalue
            checkValue += letterNumeric * (7 - i);
        }
        for (i = 3; i < 6; i++) {
            // Multiply first three numbers by 7-i and add to the checkvalue
            checkValue += NHI[i] * (7 - i);
        }
        // Apply modulus 11 to the sum of the above numbers (checkValue)
        var checkSum = checkValue % 11;
        // If the checksum is not 0, subtract the checksum from 11
        // to create checkdigit. Mod 10 to convert 10 to 0.
        if (checkSum !== 0) {
            if (NHI[6] == (11 - checkSum) % 10) {
                // if the last digit of the NHI matches the checkdigit, NHI is valid 
                passTest = true;
            }
        }
    }
    return passTest;
}