Initial commit

.gitignore

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+npm-debug.log*
+node_modules/

README.md

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+# isni-utils
+
+Validates and generates ISNI (International Standard Name Identifier) codes
+
+## Usage
+
+Usage as a Node library:
+
+```js
+const isni = require('isni-utils');
+
+isni.validate('0000-0001-2147-8925') // true
+isni.validate('0000000121478925') // true
+isni.validate('1234-1234-1234-1234') // false
+
+isni.generate() // Generates a random ISNI code
+```

index.js

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+module.exports = {
+    validate(isni) {
+        const isniString = isni?.toString() || '';
+        const stripped = isniString.replace(/\s+/g, '').replace(/-/g, '');
+        if (stripped.length !== 16) {
+            return false;
+        }
+        const baseDigits = stripped.substring(0, 15);
+        const checksum = stripped.substring(15, 16);
+        const calculatedChecksum = calculateChecksum(baseDigits);
+        if (checksum !== calculatedChecksum) {
+            return false;
+        }
+        return true;
+    },
+    generate() {
+        const baseDigits = Math.floor(Math.random() * 1000000000000000).toString().padStart(15, '0');
+        const checksum = calculateChecksum(baseDigits);
+        return baseDigits.toString() + checksum.toString();
+    }
+}
+
+const calculateChecksum = (isniBaseDigits) => {
+    let total = 0;
+    for (let i = 0; i < 15; i++) {
+        total = (total + parseInt(isniBaseDigits.charAt(i), 10)) * 2;
+    }
+    const remainder = total % 11;
+    const result = (12 - remainder) % 11;
+    return result === 10 ? 'X' : result.toString();
+}