URL Decoder (Full Percent-Decoding) Decode percent-encoded URL strings back to readable text.

Under the hood, it relies on the `decodeURIComponent()` function from the browser's API to handle percent-decoding according to RFC 3986 standards. This process involves replacing each `%HH` triplet with its corresponding byte value using Unicode code points, then interpreting the resulting byte sequence as UTF-8 encoded text. To ensure correct handling of form-encoded data, a regular expression is used to replace all occurrences of `+` with spaces before passing the input string to `decodeURIComponent()`. This preprocessing step is crucial for accurate decoding of query strings and API requests that contain form-encoded parameters.

The tool's implementation uses React's `useCallback()` hook to memoize the decoding function, preventing unnecessary re-renders when the component receives new props. When an invalid URL-encoded string is passed to it, a try-catch block catches the resulting error and returns an error message instead of throwing an exception. This approach allows for more robust error handling compared to traditional URIError exceptions. The `TextToolLayout` component from the React library handles rendering the input field, output area, and other UI elements, while the decoding logic is encapsulated within the `onProcess()` function.

In terms of data structures, it operates on strings exclusively, using JavaScript's built-in string manipulation methods to preprocess and decode the input. The regular expression `/+/g` used for replacing plus signs with spaces utilizes a global flag (`g`) to ensure all occurrences are replaced, not just the first one. By processing the input entirely on the client-side using React and browser APIs like `decodeURIComponent()`, it achieves efficient decoding of URL-encoded strings without relying on server-side resources or external libraries. The resulting decoded text is then rendered in the output area as a UTF-8 encoded string, allowing developers to inspect and work with the original data.