Dart 1.0 launch is imminent
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There isn't anything super amazing about this language from a language perspective, but I think you need to look at what Dart really brings to understand why it may be a nice alternative to JS.
* Optional typing. While typing data is completely ignored at runtime, even in the DartVM, it can help a lot for tooling if you are working on a large project. If you don't care about typing, you can just use "var" for everything.
* Batteries Included: IDE, package manager, core libraries. This means you get decent IDE to start coding in. If you don't like Dart's eclipse-based IDE, JetBrains has been maintaining a Dart plugin for their IDE (IntelliJ or Webstorm). The core library includes a lot of useful classes (not to the level of Java, but definitely has a lot of useful default packages). The package manager is nice to ship with the product as well to maintain use of 3rd party libraries.
* Nice development story. Sure, no shipping browser has the DartVM in it, but when you are doing initial development, you can use Dartium (chormium build with the DartVM in it) to do fast, iterative development. When you need to cross-browser test, you deploy to JS and see how things go.
* Speed. If/when the DartVM starts to ship in Chrome, it should help performance of apps that ship as Dart code. Specifically the runtime performance can be better as their DartVM doesn't have to support a lot of legacy syntax/behavior that JS VMs have to worry about. Along with that, the DartVM supports Snapshots. These are basically a heap dump of an application right before main() is run. This allows Dart apps to start up a lot faster on subsequent reloads.
(I do have to deal with the fun that is Perl on a daily basis, but I'm still more a fan of Java style OOP).
Also, my entire professional career has been working on projects that are worked on by 30+ people with a very large code base. When you have large teams using a language that doesn't enforce strict structure, you tend to miss things that could have easily been found at compile-time with proper tooling. This can be accomplished in languages like Javascript, but it requires strict internal controls. Having the language give you that kind of support out of the box is nice to have.
To each his own, this does fill a need. The conspiracy aficionados Dart attracts however sure are unfortunate.
While I'm impressed with Go, I personally find Dart far more accessible. Because of my Java background it makes a lot more intuitive sense, and its target user-group is web developers. Go has an immense amount of power for the same group, but unfortunately it's marketed as a system-level language (which I understand it does very well, but isn't of interest to me) and is similarly inaccessible. If Go focused more on presenting itself (particularly in the tutorials/learning aids area) as a language for web development, I think it'd stand an excellent chance of stealing market (and mind) share from Node, and possibly even Dart on the server-side.
It's possible they will pursue this course in the future as it has become quite obvious that their intended user-group (C++/low-level guys) aren't generally that interested in a replacement language.
Like many others who've kept Dart on their radar, I've been waiting to get serious about Dart until it stabilized at 1.0. Now that its 1.0 release is imminent, I'm likely to move into Dart in a big way. JS is fine and works very well for a lot of folks, but Dart is much more appealing (a lot more sane) to me.
I suspect when it's been post-1.0 as long as Go and Angular it'll be as popular. In other words, give it a year or two.
I don't know if/when this will show up in mainstream Chrome builds, but technically it's been possible for a while now.
I'm not as worried about the file size as I am about the future performance of the browser itself, and becoming too complex and with too many bugs because of that.
Chrome for Android has already gotten a lot of flack for being too bloated and slow (as an app) compared to the previous Android browser, which was made for mobile from day one, while Chrome for Android just seemed almost fully ported over, which I think hurt its performance on mobile, and they're still working on fixing that and optimizing it.
You seem to be implying Dart's semantics are influenced by JavaScript's because it compiles to it, but that's not the case. It's true for CoffeeScript because CoffeeScript doesn't try to add semantics to JavaScript, it's just a syntactic translation.
Yes, there is an aspect of "works best in Chrome" performance-wise, since Dart VM will be faster than dart2js, but if you were sold on Dart before hearing about dart2js, I don't know why that would make you change your mind. You were hoping for a JavaScript replacement, and Dart is exactly that. Compiling to JavaScript is just something to ease the transition.
https://news.ycombinator.com/item?id=6695904
I apologize if it was too meta.