PDF Delete Pages Delete PDF pages.

The tool works under the hood by utilizing client-side JavaScript with React, where memoization is used to optimize performance through the `useMemo` hook. When a PDF file is dropped into the interface, it is loaded into memory using the `PDFDocument.load` method from the `pdf-lib` library, which allows for the extraction of page count and other document properties. The page specification input is then parsed into a Set of 0-based indices using the `parsePageSpec` function, which splits the input string by commas and processes each token to determine the pages to be deleted.

The `parsePageSpec` function handles both individual page numbers and ranges, such as "1-5" or "3-5, 8", by splitting the range into start and end values and iterating over the range to add each page index to the Set. The resulting Set of page indices is then used to create a new PDF document with the specified pages removed, using the `PDFDocument.create` method and the `copyPages` method from `pdf-lib`. The new PDF document is saved to a Blob object, which is then converted to a URL using the `URL.createObjectURL` method, allowing the user to download the updated PDF file.

The tool also utilizes various browser APIs, such as the Clipboard API, to enable features like downloading the resulting PDF file. Additionally, the interface is built with a responsive UI, ensuring that it adapts to different screen sizes and devices. The `useCallback` hook is used to memoize functions like `handleFile`, `process`, and `download`, which helps prevent unnecessary re-renders and improves performance. Overall, the tool's architecture relies on a combination of React hooks, browser APIs, and libraries like `pdf-lib` to provide a seamless and efficient user experience.