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Comment by dang | Hacker News Reader

That sounds promising. Is it possible to send messages between the tabs? My Chrome extension does that like crazy.

Forgive me for hijacking this thread into technical support territory, but I've found documentation on this stuff hard to come by.

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Re: hijacking.

It's OK, I'm sure the mods will take care of it.

EDIT: I know this isn't reddit but I couldn't resist. Dan it's admirable how nice and down-to-earth you are in spite of all the stuff you see here everyday...huge thanks for all your work in making HN what it is.

You can do that with local storage. Not sure if there's an existing project that simplifies the process but the general idea is to use it as a hash map that's available to all tabs attached to the same domain.

You'd have to synchronize things yourself to prevent tripping over yourself. Ditto for firing off functions in response to events (i.e. Poll loop and fire handler).

So just straightforward cache invalidation-style stuff?

Yes: there's a couple ways to do it, but the most common is to use localStorage and the 'storage' event, which will post in every open window when you modify localStorage.

It's very easy to check for localStorage support (some people disable it just like cookies) and it works, I think, everywhere except Opera, in almost every mainstream version.

(I use it a bunch).

Works in Opera too so far as I can see: http://caniuse.com/#feat=namevalue-storage

it used to be possible to simply access the other DOM via window. As long as they where in the same context (basically domain)

Edit:

Yep

  w2 = window.open('/');
  w2.document.click()

Is fine if complying with the sameOrigin policy

https://developer.mozilla.org/en-US/docs/Web/API/Window/open

>Is it possible to send messages between the tabs?

Save objects to local storage:

localStorage.name = "dang";

alert(localStorage.name);

yes, the localstorage is the way to go

You save stuff to localstorage in one tab, and in other tab you listen to "storage" event:

    window.addEventListener('storage', function() {..})

[0] https://developer.mozilla.org/en-US/docs/Web/API/Web_Storage...

[1] https://developer.mozilla.org/en-US/docs/Web/Events/storage

Another option is shared web workers, though I never used it.

[2] http://stackoverflow.com/questions/12107424/communication-be...

[3] https://developer.mozilla.org/en-US/docs/Web/API/SharedWorke...

I confused things in my other comment (I deleted it)

Also something that could be promising depending on the circumstances you could use a shared webworker. They allow you to share a webworker script across multiple tabs. I think you have to be from the same domain, but I assume that you have to do that for local storage.

Yep, using w.postMessage()

That's pretty close to what I'm doing now, but I use chrome.tabs.sendMessage. Thanks; I'd love to get this working without that dependency.

AFAIU postMessage() works between the frames (even cross-origin) within a tab. If you need communication between the tabs, localStorage is the way to go

`postMessage()` works between ANY window references -- tabs or frames. As long as you have a reference to the window (which you will if you call `window.open()`) then you can post messages to it.

Can you elaborate on what the extension does? e.g., for moderating comments more effectively, for reading deeply nested comments, some kind of internal actions we don't have access to, etc.

Hmm, let's see. It does a lot of moderatory things, but general readery things include highlighting stories or commments and jumping to related pages (e.g. the story url, the thread url, the user's profile page, the user's comments page, other stories from that domain), opening and closing those tabs; navigating up and down comment trees (go to parent, go to prev/next sibling); marking stories or comments as 'seen' and thus hiding them, but keeping track of whether 'seen' items have changed and displaying how they changed; finding comments that match regexes and highlighting the matches; if a comment contains a url, open that url in a new tab; jump around between open tabs; go to the root url of a comment (i.e. the original story item); select text and open tabs based on that text; show HN search results in the form of an HN story list that looks like the front page; take various actions based on what's in the clipboard, or copy HN urls or titles to the clipboard; filter stories or comments being displayed according to various criteria; upvote or flag a post; go to the internet archive for a url; show the current rank of a story on pages other than the front page; request the 'more' url at the bottom of a page and inline its results instead of navigating to it. Edit: I forgot one of my favorites, which is aligning the current selection to the center, top, or bottom of the window, a la ctrl+L in Emacs.

It's all done by keyboard shortcuts, which means the mapping to keys is pretty complicated and not as consistent as I'd like.

Edit: It's also written in a Lisp we made that only three of you have ever heard of :)

I recommend you not let the perfect be the enemy of the good on this, and go full-on Dwarf Fortress with this, bizarre undocumented keybindings and all.

That's a great list. Some of these specific features I've considered building as an extension from a reader perspective. Especially for dealing with deeply nested comments, and "find the top HN discussion if any for this URL that I'm currently on".

And you can compile that Lisp to JavaScript to build the Chrome extension?

Yes, the Lisp exists so we can write JavaScript without having to leave the Garden of Eden.

The extension is written in Arc? That's...not a use of Arc I expected. Did you have to change the language much to do it?

I'm guessing it's written in the Lisp Dan built for Skysheet.

Wow! Do you know of anything more written about it? I can't seem to find any information.

https://news.ycombinator.com/item?id=11673343

\o/

One of them. :)

Dan and Scott, though, and in this case mostly Scott.

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