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When the tooling works, it has some really great things mostly related to IDE functionality. But when it doesn't it's a nightmare. It's more than just quirks. It's not hyperbole either, I just had a different experience with it than you.

I sincerely hope it doesn't die on you after you convert your codebase. I wouldn't wish that on anyone.

It's far worse than "the definitions for external JS libs are not perfect;" it's that the TypeScript compiler throws a tantrum when they aren't perfect, which is >50% of the time, to be generous. AllowJS is relatively recent and didn't exist when I started using it - which is shocking, because integration with the JavaScript ecosystem was a major selling point (just check the TS project site's front page). CheckJS is very recent and VS2017 doesn't even support it yet - for a language whose main selling point is tooling support, it's shocking that VS2017 doesn't let users update their TS version.

Another selling point listed on the front page of its website: ES2015 features. Except it doesn't provide Promises, Map, Sets (and I can't remember if they added Object.Assign support, but it also was not supported when I was using it). When you provide your own polyfills, TSC complains unless you provide typings and add specific config values informing it what you polyfilled.

Its 3 main selling points were JavaScript ecosystem integration, ES2015 features, and tight tooling/IDE integration. Each of those things failed me when I used it. The IDE part hurt me the worst, preventing my project from compiling altogether for a while. Every one of its main selling points has been a pain point for me.




> Except it doesn't provide Promises, Map, Sets (and I can't remember if they added Object.Assign support, but it also was not supported when I was using it). When you provide your own polyfills, TSC complains unless you provide typings and add specific config values informing it what you polyfilled.

I think you may have misunderstood what Typescript is and isn't.

It isn't meant to provide polyfills, it is only supposed to handle the grammar of the language that needs to be transpiled.

That's why you have the two following settings: - target : Which version of the grammar will be available at runtime (eg. classes, async, ...), that's the part used by the transpiler - lib : Which libraries (eg. promises, maps, sets, ...) you know will be available at runtime (only used for type-checking)

Using a polyfill is really easy if you are using the right value for "lib" since the it will have the same signature as the real method: simply import it once in your project.


That's fair enough. My actual main issue with this is that TS was hostile towards any external JS libraries, especially before 1.8, but still sporadically in 1.8+, and that affected polyfills too. I also had serious issues importing external libraries that provided their own polyfills.

It was sort of a catch-22 that it didn't like JS yet expected JS polyfills. This has been greatly improved but it took far too long for a project that purports to be a part of the JS ecosystem, which raises questions and I must admit, makes me cynical about whether this was a business tactic.

I've now written many replies with elaborations and clarifications of my criticisms, so it may seem like I'm excessively negative about TS. I actually really like the language itself, especially the static type checking, which is the one main selling point. The OO language features are great because they're optional. I just think everything around the language is rough, and if you're unlucky with it, it can ruin the whole experience.

I remember that at one point, people would declare `require` and use `import whatever = require('whatever')` for npm libraries. This thing was for the longest time absolutely hostile towards JS, and some remnants of that philosophy remain to this day.

I have not forgotten being told to write what amounts to C header files, for JavaScript, in order to allow TSC to play nice with the ecosystem! That was definitely hubris.


> I sincerely hope it doesn't die on you after you convert your codebase. I wouldn't wish that on anyone.

Pretty sure the product I'm working on will die long before TS :) I think TS is here to stay, and if MS decides to drop it, for whatever crazy reason, then the source code is available. And there is still the option to take the compiled JS code, and hope for some "cleanup" tool, like Decaffeinate, or gradually clean it up yourself... Not nice I agree, but I see no dead end here.

> it's that the TypeScript compiler throws a tantrum when they aren't perfect, which is >50% of the time, to be generous.

Really not sure why our experience differs so much from yours. Like I mentioned, we use a shitload of popular libraries, and for every single one there was a d.ts file available. If I see a definition that is wrong/outdated/broken then I create a fork, fix it and make a pull request. Doesn't usually take longer than a few minutes (depending how outdated the definition file is). Instead of complaining, I try to actively help improve the situation. Most of those d.ts files are written by normal developers in their spare time, after all, so it doesn't help to curse those people.

> Another selling point listed on the front page of its website: ES2015 features. Except it doesn't provide Promises, Map, Sets (and I can't remember if they added Object.Assign support, but it also was not supported when I was using it). When you provide your own polyfills, TSC complains unless you provide typings and add specific config values informing it what you polyfilled.

Yeah it's weird, and I don't get it either. Our solution to this is to run the compiled JS code through Babel. We use webpack for this and it's pretty much hassle free. On the other hand, for someone new to TS/JS this may not be obvious. So I agree there is a tooling problem in this regard, but once you know about it, it's a non issue. So yeah, it would've been nice if the TS compiler did properly polyfill things.

And don't get me even started on Visual Studio. I hate to work with it. It's nice for small projects/solutions, but we have a rather big solution, with a couple "Azure cloud classic" projects, and the whole thing is soooo fucking slow. Changing a single value in a ServiceConfiguration.cfg file will freeze VS for almost a minute, for example. There is lag and delays everywhere. The "TypeScript for Visual Studio Extension" was also very problematic, so we disabled all TS features in VS. We use Sublime/VS Code only since a very long time to edit our JS code. VS is a sad joke for a frontend developer.


I'm absolutely fine with external libs not being typechecked if there's no d.ts. The issue is it literally didn't support this scenario until 1.8 (when AllowJS was added). To me, this is the biggest tell that there's something fundamentally wrong with TS's design priorities. How could it not support JavaScript libraries for so long?

Here is one of numerous posts mirroring one of the module resolution issues that has plagued my project: https://stackoverflow.com/questions/39957100/visual-studio-2...

There are equivalent reports on GitHub and elsewhere on the net, as well as numerous related but separate issues.

IDEs from the same organization that sponsors TS don't even work reliably with it. Note one of the responses: "try VSCode." Indeed, VSCode works for me on the exact same code.

Currently I'm doing the same thing as you: running the TS output + the non-TS codebase through a giant blender of browserify + babel.

At one point, I would use --outfile, which makes TSC bundle all your files and dependencies. Neat, right? Nope - it gets the order of the dependencies wrong, which you find out later, at runtime. The maintainers on GitHub said "don't use outfile."


Are you really sure it wasn't possible to use external libs prior to the allowJs flag? I vividly remember a colleague fiddling around with TS when 1.0 was released, and we had discussions about definition files and how lacking they were. But I'm pretty sure he was able to declare an external module as "any" in a d.ts file, and then he could simply require it and use it without type information. As far as I know, the allowJs flag allows you to import/require your own .js files (as opposed to external modules), before that this wasn't possible apparently. Without this functionality I don't know how it was possible to gradually convert a code base to ts. We probably wouldn't be using TS now without the allowJs flag. I guess we are lucky to have picked up TS in a state where most of the early issues have been resolved (not saying there are no issues left).

I totally understand your frustrations with VS, though most of the problems you mentioned seem to be related to the TS integration in VS, and not with TS directly. But issues like yours are the reason why I lost hope in VS. I try to use it as little as possible.


I'm not sure if it was impossible, just that it was a giant mess and it utterly failed to work properly for me. Broadly speaking, point is just that TS treats JS as a second class citizen, and it adversely affects the day to day usability.


it seems reasonable that it didn't allow it before the language designers explicitly created a flag for it.

That doesn't mean some enterprising soul wasn't able to make it work, but it does mean it wasn't officially supported.




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