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Why is JavaScript single-threaded?

I just read through this piece about callback-less JavaScript coding, and it raises a question I've never seen answered, that I've been puzzled about ever since I learned that there are just a couple of threads in a JavaScript app running in the browser.

The question is this -- why?

It's been a long time since I worked in an environment that had such a constraint.

I kept looking for the JavaScript verb that forks off another thread. Until I realized there was no such verb. Why not just relax the rule and let a JavaScript app spawn a certain number of threads. And if it needs more, ask the user if that's okay. Like getting more memory in an iPad app.

It crossed my mind that this might be a way for a web page to crash your browser. But I'm pretty sure I can already do that with a simple loop that does nothing and never terminates.

while (true) {}

Anyway -- if you have any idea please post a comment.

8/15/2013; 5:20:57 PM

Feedly will support dynamic OPML

Just got a response from Edwin Khodabakchian of Feedly saying they will support dynamic OPML in version 18 or 19. This is very good news for Feedly users, of course, and for people and organizations with domain expertise (curators) and app developers.

It should be possible to hook up new subscription services to Feedly, and because they are using an open format, the same lists will work equally well with any other feed reader or aggregator that supports OPML.

Thanks Edwin, this is very exciting!

PS: If you're a developer, please support the feature so your users can benefit from reading lists produced by experts and by recommendation engines.

PPS: And if you're a user, send a pointer to this post to the developer of your favorite feed reader asking that they support dynamic OPML too.

8/15/2013; 3:17:43 PM

Feed reader developers -- here's an easy way to differentiate your service and have your users love you even more

You all read and write OPML subscription lists, right?

Let's go one step further, and let users subscribe to OPML subscription lists.

How would that work?

Each such list is readable over the Internet, the same way RSS feeds are.

As often as you would read a feed, read the OPML file.

If there's a new feed in the list, and the user is not subscribed to it, add it to their feed list.

If a feed has been removed from the list, and the user was not previously subscribed to it, remove it from their feed list.

Why is that cool?

It means the list can be maintained by another piece of software, or by another human being. A domain expert, for example. Ezra Klein might keep a list of feeds a good liberal blogger would read. Or George Will would keep a list for plutocrats.

Spotify could give you a list of feeds to follow for your favorite bands, and that list would change as your musical tastes evolve.

The New York Times could provide a list that tracks the major political issues, and when one dies out, it would be replaced by another.

Jay Rosen, Doc Searls. Josh Marshall, John Gruber, The Economist -- they could all provide opinionated selections of feeds you will find essential.

You could have lists maintained by applications designed to track your interests and interests of thousands of other people, and add feeds to your list based on what those people are following.

In other words there are whole new areas of technology waiting for you to add this feature!

The pitch

Now why should you do it?

Because it's the kind of feature that will appeal to the early adopters.

Reporters, editors, bloggers, podcasters, super-fanboy types.

People with itchy feed-reading fingers. Whose palms sweat when their favorite feeds update. Who love the idea of getting new feeds without doing any work. They want to know what's up before anyone else does.

These people in turn influence lots of other people. They will talk about your product, and that will build your presence, and help other people learn how cool your stuff is.

Why does Dave want it?

I want to provide a curated feed list for people who read my blog.

I already have it, but I'm looking for an excuse to clean it up!

Just do it!

It takes a couple of days at most.

The hardest part is maintaining a reference count on feeds, so you know when to remove it from the user's main list (it might be in two or more lists, so having it disappear from one just means its reference count goes down).

And when you do it, let me know so I can sing your praise.

Update

Feedly is going to do it in an upcoming release.

8/15/2013; 8:15:14 AM


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