Data update

Task/Verhoeff-algorithm/JavaScript/verhoeff-algorithm.js

@@ -0,0 +1,80 @@
+const multiplicationTable = [
+  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
+  [1, 2, 3, 4, 0, 6, 7, 8, 9, 5],
+  [2, 3, 4, 0, 1, 7, 8, 9, 5, 6],
+  [3, 4, 0, 1, 2, 8, 9, 5, 6, 7],
+  [4, 0, 1, 2, 3, 9, 5, 6, 7, 8],
+  [5, 9, 8, 7, 6, 0, 4, 3, 2, 1],
+  [6, 5, 9, 8, 7, 1, 0, 4, 3, 2],
+  [7, 6, 5, 9, 8, 2, 1, 0, 4, 3],
+  [8, 7, 6, 5, 9, 3, 2, 1, 0, 4],
+  [9, 8, 7, 6, 5, 4, 3, 2, 1, 0],
+];
+
+const inverse = [0, 4, 3, 2, 1, 5, 6, 7, 8, 9];
+
+const permutationTable = [
+  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
+  [1, 5, 7, 6, 2, 8, 3, 0, 9, 4],
+  [5, 8, 0, 3, 7, 9, 6, 1, 4, 2],
+  [8, 9, 1, 6, 0, 4, 3, 5, 2, 7],
+  [9, 4, 5, 3, 1, 2, 6, 8, 7, 0],
+  [4, 2, 8, 6, 5, 7, 3, 9, 0, 1],
+  [2, 7, 9, 3, 8, 0, 6, 4, 1, 5],
+  [7, 0, 4, 6, 9, 1, 3, 2, 5, 8],
+];
+
+
+function verhoeffChecksum(number, doValidation, doDisplay) {
+  if (doDisplay) {
+    const calculationType = doValidation ? "Validation" : "Check digit";
+    console.log(calculationType + " calculations for " + number + "\n");
+    console.log(" i  ni  p[i, ni]  c");
+    console.log("-------------------");
+  }
+
+  if (!doValidation) {
+    number += "0";
+  }
+
+  let c = 0;
+  const le = number.length - 1;
+
+  for (let i = le; i >= 0; i--) {
+    const ni = parseInt(number.charAt(i));
+    const pi = permutationTable[(le - i) % 8][ni];
+    c = multiplicationTable[c][pi];
+
+    if (doDisplay) {
+      console.log(`${String(le - i).padStart(2)}${String(ni).padStart(3)}${String(pi).padStart(8)}${String(c).padStart(6)}\n`);
+    }
+  }
+
+  if (doDisplay && !doValidation) {
+    console.log("inverse[" + c + "] = " + inverse[c] + "\n");
+  }
+
+  return doValidation ? c === 0 : inverse[c];
+}
+
+
+function main() {
+  const tests = [
+    ["236", true],
+    ["12345", true],
+    ["123456789012", false],
+  ];
+
+  for (const test of tests) {
+    let object = verhoeffChecksum(test[0], false, test[1]);
+    console.log("The check digit for " + test[0] + " is " + object + "\n");
+
+    for (const number of [test[0] + String(object), test[0] + "9"]) {
+      object = verhoeffChecksum(number, true, test[1]);
+      const result = object ? "correct" : "incorrect";
+      console.log("The validation for " + number + " is " + result + ".\n");
+    }
+  }
+}
+
+main();