Question 174301 in Javascript Question posted in
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Javascript – How to calculate the check digit according to ISO 6346

How to implement the check digit algorithm specified in ISO 6346 Freight containers — Coding, identification and marking?

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  1. Chosen as BEST ANSWER
    0

    Implementation in JavaScript:

    function checkCscDigit(csc) {
    csc = csc.toUpperCase().replace(/[^A-Z0-9]+/g, '');
    if (csc.length < 10) return [ null, null ];

    // Retreive the check digit from the string (11th character.)
    let check = (csc.length == 11 && !isNaN(csc[10])) ? parseInt(csc[10]) : null;

    // Calculate check digit.
    var sum = 0;
    for (let i = 0; i < 10; i++) {

        // Convert letters to numbers.
        let n = isNaN(csc[i]) ? csc.charCodeAt(i) - 55 : parseInt(csc[i]);

        if (n) {
          // Digits 11, 22, 33 are omitted.
            n += Math.floor((n-1) / 10);

          // Sum of all digits multiplied by weighting.
          sum += n * Math.pow(2, i);
        }
    }

    // Modulus of 11, and convert 10 to 0.
    let calculation = sum % 11 % 10;

    return [ check, calculation ];
}

    Usage:

    let [check, calculation] = checkCscDigit('ABCD 123456 [0]');

if (calculation !== null) {
    console.log(check, calculation)
    if (check === calculation) {
        console.log('Valid!');
    }
}

    Here, check is the 11th character extracted from the string, which is the check digit. calculation is the check digit calculated from the first 10 characters in the string. If these two match, then the string is valid.

    JSFiddle


  2. 0

    Alternatively, using map and reduce.

        let calculation = Array.from(csc.slice(0, 10))
      .map(c => isNaN(c) ? c.charCodeAt(0) - 55 : parseInt(c)) // To digit.
      .map(d => d + Math.floor(Math.max(0, d-1) / 10)) // Omit multiples of 11.
      .map((d, i) => d * Math.pow(2, i)) // Weighting.
      .reduce((a, b) => a + b) // Summation.
      % 11 // Modulus of 11.
      % 10; // Convert 10 to 0.

    (Where csc is a valid 11 digit string 'ABCD1234560'.)

    JSFiddle

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