I disagree. Typescript is just ECMAScript 6, with type annotations. Most of the differences come from the language changes (ES5 -> ES6), than the superset that Typescript explicitly adds.
> Typescript is just ECMAScript 6, with type annotations.
Then it's not "just ECMAScript 6", is it? Anyway, I'm not saying TypeScript doesn't have merit--in fact, I'm considering using it in my next web app. I'm just saying that using TypeScript is a tradeoff that's not without drawbacks, since you're now dependent on a new set of tools and new additions to the syntax (which means, for instance, that your editor/IDE has to specifically support TypeScript). You could say the same about ES6, but at least the latter is at some point going to be standard among browsers (and the tools won't be needed).
It's not "Javascript with a bunch of proprietary extensions", either. Type annotations can't be the difference between understanding code in Typescript if you understand Javascript.
You have a point about tooling, but you would have the same problem if you had a project on visual c++ 6 and upgraded to c++/14, and again, you didn't mention it.
All of this is in spite of the fact that ES6 nearly had optional type annotation in the same syntax that Typescript does, along with many other Javascript derivations that use the same type annotation syntax (Actionscript and Atscript that I know of).
I don't see what the trade-off is. You can just take the transpiling output and go home if you want. Out of all the languages that transpile to JavaScript, Typescript is probably the least risky because it is just JavaScript if you want it to be just JavaScript.
The tradeoff is having to use a language other than JavaScript, which entails having to use a transpiler in the first place, versus just writing plain old JS.
Then it's not "just ECMAScript 6", is it? Anyway, I'm not saying TypeScript doesn't have merit--in fact, I'm considering using it in my next web app. I'm just saying that using TypeScript is a tradeoff that's not without drawbacks, since you're now dependent on a new set of tools and new additions to the syntax (which means, for instance, that your editor/IDE has to specifically support TypeScript). You could say the same about ES6, but at least the latter is at some point going to be standard among browsers (and the tools won't be needed).