Verify EAN & UPC Barcode Check Digits Validate barcode formats including EAN-13, EAN-8, UPC-A, and UPC-E with check digit verification.

The tool works by first cleaning the input string of any non-digit characters and then checking its length to determine the barcode format. It uses a switch statement to handle different lengths, corresponding to EAN-8, UPC-A, EAN-13, and GTIN-14 formats. For each format, it applies a specific validation algorithm, such as the validateUPC or validateEAN13 functions, which calculate the check digit using an alternating-weight sum of the digits. The tool also extracts additional information, like the country or region prefix for EAN-13 barcodes, by parsing the first three digits and comparing them to a set of predefined ranges. This process relies on JavaScript's built-in string manipulation and arithmetic capabilities, as well as React's useState and useCallback hooks for managing state and handling user input.

The validation algorithms used are based on industry-standard formulas for calculating check digits, which involve multiplying each digit by a weight (either 1 or 3) and summing the results. The tool then compares this calculated check digit to the actual check digit in the input string to determine whether the barcode is valid. In the case of GTIN-14 barcodes, it uses a similar calculation as EAN-13 but with an additional packaging indicator digit. The tool's user interface is built using React and renders the validation results, including any error messages or detailed feedback, in a glass-card layout with interactive buttons for validating and clearing input. The SAMPLES array provides pre-defined test cases for demonstrating the tool's functionality with different barcode formats.