feat: Add support for UPC

src/modules/commerce/index.ts

@@ -84,6 +84,8 @@
  * For a department in a shop or product category, use [`department()`](https://fakerjs.dev/api/commerce.html#department).
  *
  * You can also create a price using [`price()`](https://fakerjs.dev/api/commerce.html#price).
+ *
+ * To work with product identifiers, generate an ISBN via [`isbn()`](https://fakerjs.dev/api/commerce.html#isbn) or a 12‑digit UPC via [`upc()`](https://fakerjs.dev/api/commerce.html#upc). You can compute a UPC check digit using [`calculateCheckDigit()`](https://fakerjs.dev/api/commerce.html#calculatecheckdigit).
  */
 export class CommerceModule extends ModuleBase {
   /**
@@ -349,4 +351,76 @@
 
     return data.join(separator);
   }
+
+  /**
+   * Returns a valid [UPC‑A](https://en.wikipedia.org/wiki/Universal_Product_Code) (12 digits).
+   *
+   * When a `prefix` is provided, it is sanitized to digits and padded with random
+   * digits so that the body has 11 digits. The 12th digit (check digit) is computed
+   * using the Modulo 10 algorithm.
+   *
+   * @param prefix Optional numeric prefix for the UPC body (0–11 digits). Non‑digits are ignored.
+   *
+   * @returns A 12‑digit UPC‑A string.
+   *
+   * @throws {FakerError} If `prefix` contains more than 11 digits after sanitization.
+   *
+   * @see calculateCheckDigit
+   *
+   * @example
+   * faker.commerce.upc() // '036000291452'
+   * faker.commerce.upc('01234') // '012345678905'
+   *
+   * @since 10.1.0
+   */
+  upc(prefix = ''): string {
+    const clean = (prefix || '').replaceAll(/\D/g, '');
+    if (clean.length > 11) {
+      throw new FakerError('Prefix must be at most 11 numeric digits');
+    }
+
+    const remaining = 11 - clean.length;
+    const rand = Array.from({ length: remaining }, () =>
+      this.faker.number.int({ min: 0, max: 9 })
+    ).join('');
+
+    const body = `${clean}${rand}`; // 11 digits
+    const check = this.calculateCheckDigit(body);
+    return `${body}${check}`; // 12-digit UPC-A
+  }
+
+  /**
+   * Calculates the check digit for a UPC‑A using the Modulo 10 algorithm.
+   *
+   * @param digits The first 11 digits (UPC body) as a numeric string.
+   *
+   * @returns The check digit (0–9).
+   *
+   * @throws {FakerError} If `digits` is not exactly 11 numeric characters.
+   *
+   * @see upc
+   *
+   * @example
+   * faker.commerce.calculateCheckDigit('12345678901') // 2
+   * faker.commerce.calculateCheckDigit('01234567890') // 5
+   *
+   * @since 10.1.0
+   */
+  calculateCheckDigit(digits: string): number {
+    if (!/^\d{11}$/.test(digits)) {
+      throw new FakerError(
+        'calculateCheckDigit expects exactly 11 numeric digits'
+      );
+    }
+
+    let sum = 0;
+    let idx = 0;
+    for (const digit of digits) {
+      const n = Number.parseInt(digit, 10);
+      sum += n * (idx % 2 === 0 ? 3 : 1);
+      idx++;
+    }
+
+    return (10 - (sum % 10)) % 10;
+  }
 }