And if one wants to list the content of the archives, zip is better and orders of magnitude faster, as it also has a "central directory" so one doesn't have to read the whole archive to get the list.

I've used that "central directory" approach even over the internet with a great success (downloading just that segment instead of the whole archive to get a list of what is inside).

But how did you make a bookmarklet to produce a zip archive, even non-compressed?

I assume that the author concatenated the image blobs into one buffer, then manually generated a file table. I believe there is a way to offer a “Download” button for buffer objects in JS.

> But how did you make a bookmarklet to produce a zip archive, even non-compressed?

Not quite sure I understand the question. Bookmarklets are bookmarks which contain JavaScript code, for example:

javascript:alert('Hello, World!');

You can put that in a link

<a href="javascript:alert('Hello, World!');">Bookmarklet</a>

and then you can right-click the link to bookmark it. Now, when you want to run that JavaScript code on some website, visit the website and click on the bookmark.

I know bookmarklets basics. What I wanted to know is which API calls you used inside of the < 2000 character bookmarklet to achieve the functionality you described. I also believed that the bookmarklets are limited to the security context of the web page and I don't understand how you did all that, if I understood you correctly you are generating zip out of the images from the web page using only the bookmarklet?

Do you, or do you do something much simpler?

> I know bookmarklets basics. What I wanted to know is which API calls you used inside of the < 2000 character bookmarklet to achieve the functionality you described.

To create the archive data, I used an Uint8Array where I wrote the bytes into.

To download the images, I used XMLHttpRequest.

> I also believed that the bookmarklets are limited to the security context of the web page

That seems to be true unfortunately. However, besides the images on the same domain, it should also be possible to download some more images from other domains by allowing cross origin requests if the remote server cooperates and sets the respective header. but I have not looked into that yet.

The bookmarklet is here if you have more questions: https://github.com/983/FileDownloader

It is a bit larger than 2500 characters now since previously the code was optimized for size. Now it is slightly more readable.

That's fantastic, and with HTTP range you could get individual files from inside the zip, effectively creating a just in time zip browser.

Being able to download individual parts seems good: you could have seperate sha256 info for files for instance.

This is such a great idea! You don't need compression because images on the web are generally compressed already. Can you share any of your code that does this?

Sure! Here it is: https://github.com/983/FileDownloader

Can you post your bookmarklet? I tried making a similar thing (using TamperMonkey) and ran into browser security restrictions preventing downloading of the files.

I tried TamperMonkey for a different project, but it kept deleting my scripts, so I haven't pursued it any further.

Bookmarklets are executed in the context of the currently opened website, so downloading images from the same origin is usually not a problem. What can be an issue are remote images. I tried setting `Access-Control-Allow-Origin: *`, but then other downloads would fail, so I left it as it was since it worked for the websites I was interested in.

Here is the code: https://github.com/983/FileDownloader