XOR Cipher — Encrypt & Decrypt Online Encrypt and decrypt text using XOR cipher with a repeating key.

The tool works by using the JavaScript `charCodeAt` method to get the ASCII value of each character in the input string and then performing a bitwise XOR operation with the corresponding key byte. The result is converted to a hexadecimal string using the `toString(16)` method and padded with zeros if necessary. When decrypting, the process is reversed by parsing the hex bytes back into integers, performing another XOR operation with the key bytes, and converting the resulting ASCII values back into characters using the `String.fromCharCode` function.

In encrypt mode, it splits the input string into individual characters, maps over each character to perform the XOR operation, and joins the results back together as a space-separated hex string. The React library is used to manage state changes when switching between modes or updating the key, with the `useState` hook storing the current key and mode, while the `useCallback` hook memoizes the processing function to prevent unnecessary recalculations.

The tool's use of modulo arithmetic ensures that the key cycles back to its beginning once it reaches the end, allowing keys shorter than the input string. This cycling behavior is implemented via the expression `i % key.length`, which calculates the index of the current key byte based on the position of the character being processed. The resulting hex output can be easily shared or used in other applications that support hexadecimal data formats.

Error handling is performed using a try-catch block, catching any exceptions raised during processing and returning an error message if necessary. When decrypting, it trims any whitespace from the input string before splitting it into individual bytes, allowing users to enter hex strings with spaces or commas as separators. The tool's implementation relies on standard JavaScript functions like `parseInt` and `String.fromCharCode`, making it compatible with most modern web browsers that support these APIs.