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Comment by jnpatel | Hacker News Reader

also: do you use any special tools to help monitor comments, or just https://news.ycombinator.com/newcomments ?

Lots of special tools. I'm working on revising them so we can open-source the parts that are useful for general reading.

Right now it's a Chrome extension, but I'd love to serve it as plain JS. Anybody know if you can give a web app privileges to open and close tabs without making it a browser extension?

(Don't worry, btw; if we ever publish this it will be entirely opt-in.)

You can open tabs using `var w = window.open()`, and close them using `w.close()`

Only thing is users must disable popup blocking for HN, in the unlikely case that you want to open more than 2 links at once, or open links when the user doesn't click something (like onload).

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.

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.

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?

>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.

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

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.

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 :)

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.

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.

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

As parent said, you just need to store a handle to the window when you open it, and then you can use .close()

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

When opening a tab are you allowed to say where you want it in the tab order? or to change its position in the tab order later?

Thanks everyone for all the help!

Unfortunately I don't think so. In fact you can't even specify that you want it to be a tab, as opposed to a new window, but the default in all major browsers is a tab these days.

I haven't tested, but you might be able to kind of fake it by having the tab immediately before the one you want to open do the opening. That wouldn't work for tabs that have opened external sites (the stories themselves), but you could at least send a message to one of the other HN tabs telling it to open your new tab, which should give you some control.

I see. The Chrome.tabs library that I use does allow this. Your clever workaround might be enough though.

While I'm at it, is there a way to give a regular web app the kind of permissions that a Chrome extension manifest can give? It isn't just tab mechanics I need, but clipboard access and cross-domain privileges. Obviously this would still require client consent (and might still be Chrome-only) but it would be easier than an extension with all its deployment headaches.

There's a clipboard API [1] in newest browsers but browser support varies.

Regarding cross-domain, what do you want to do exactly? In general there's no built-in support at least in Firefox to override default same-origin policy, but there are Chrome/Firefox extensions that for instance inject CORS headers to each response.

Edit: In Chrome, it seems you can disable same-origin policy with command line flag [2]

[1] http://caniuse.com/#feat=clipboard

[2] http://stackoverflow.com/a/3177718/245966

I might be forgetting something but I think the main use of cross-domain privileges is so that my keyboard shortcuts still work on story pages. That way, if I open (say) a NYT article that is currently highlighted on the front page, I can jump back to the front page when I'm done looking at it.

Sounds interesting. I'd love to hear more about it sometime. Maybe even see some screenshots. You should do a Show HN post!

More details at https://news.ycombinator.com/item?id=11670562.

I'd be scared to show it as is because we get in trouble when admin-specific stuff shows up in screenshots. There once was a controversy because 'kill', 'blast', and 'nuke' links showed up in a screen shot, despite the fact that they were all defined in the version of the HN source code that pg published years ago.

A Show HN will certainly be in order if we ever publish it, though.

Since this looks like the tech support thread, I'll add that

> opening and closing those tabs when desired

will only work with window.open if the moderation tool's window owns the tabs in question. So if you open a HN tab randomly or from another site or wherever, the moderation tool won't have opened it, and so it won't be able to close it.

reddit has RES. People are used to browser extensions, and this doesn't sound like it'd cooperate too well on a phone or similar device, so I say just release the extension.

As for fun-sounding feature names, just make a help page in the extension describing how everything works. Maybe call the help page "spoilers" or something. :D

Oh and can I be the fourth person to know what Lisp you wrote this in? :D

I'm in the process of porting it from Parenscript (which we didn't create but worked on quite a bit) to Lumen (which we did create). Parenscript is better known—perhaps a dozen people have heard of it.

Wow, cool. I assume you're referring to https://github.com/sctb/lumen and https://common-lisp.net/project/parenscript/.

Thanks for the info. :)

I'm mildly curious how Lumen and Arc differ.

Lumen is an experiment in making a Lisp (or a Lisp-like thing, depending on how finicky you are about the name) in which the universal data structure isn't a list but a hashmap (hashtable, whatever you call it). That's because hashmaps have proven to be the most convenient thing for exploratory programming. So instead of 'everything is a list, including source code', you get 'everything is a hashmap, including source code'.

We also wanted it to be self-hosted, and to compile (transpile) to Lua as well as JS, in as straightforward a way as possible. JS and Lua are very close semantically, so our approach with Lumen was to take the semantic intersection of those two and then build the simplest thing we could on top of it. As a result, it's quite different from Arc, which is semantically a classical Lisp.

Here are a couple of old comments I posted about this idea, before Scott implemented it:

https://news.ycombinator.com/item?id=3291065

https://news.ycombinator.com/item?id=6544926

Technical answer to !extension: user scripting, e.g. Greasemonkey or Tampermonkey. Not quite as easy to deliver as an extension, but provides greater power such as opt-in violation of same origin policy and global variables shared across execution contexts.

The nice thing about user scripts is that there is no packaging or bundling. The advantage of Greasemonkey over Tampermonkey is it uses files rather than storing scripts in a database.

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