[DCoder]

I started using TypeScript back when it was 0.8, before it even had generics. Does that make me a fanboy? I have a project with about 45k SLOC of TypeScript (using Knockout.js for presentation). There is really no way I would maintain that same project without types.

> For my work I look at horrible code bases, perfectly typed and strictly formatted by tslint.

There is no language that can stop people from producing horrible code.

[black-alert]

> There is really no way I would maintain that same project without types.

That's bold. Do you think no developer would be able to manage it without TS? In that case you must be a fanboy!

And honestly, are you not using 'any'? And do you think your app cannot crash because of a type error at runtime? And do you trust all the third party libraries you are using that they always provide you with consistent types, also during runtime? I ask this because most TS proponents live in some kind of dream.

[DCoder]

I'm sure some developers would manage such a project without TS. Good for them. I wouldn't maintain it that way because:

1. I don't have the mental capacity to keep every single function's argument/return shape in my head, or to manually check it every time I make a change. Unit tests can't deliver 100% code coverage in practice.

2. Nor do I want to perform refactorings with stone age tools like s/setFoo/setBar/g. Setting up type information lets my IDE understand which calls to .push() deal with a native Array and which ones deal with my own class, so it can rename the latter ones when I ask. I can also use tools like "Find References" and avoid false positives.

3. I'm not a one-man-band. My coworkers need to deal with this project too, and new developers need to be introduced to it from time to time, and types serve as documentation and guard rails for them much better than jsdoc or regular comments. (This also serves as a significant barrier against using anything more esoteric like Elm, because nobody around would be familiar with it. TypeScript adds just enough syntax on top of regular JS to keep JS users comfortable.)

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I do use `any` (and `unknown`), I have no doubts that an edge case can crash my app because I didn't validate something, and I never expect third-party code to work flawlessly whether it has types or not. Rejecting TS completely because "but run time loopholes" is throwing the baby out with the bathwater (or to put it in a more hyperbolic way, being an anti-vaxxer because vaccines are not 100% safe from side-effects). TS and types are an additional safety net/force multiplier†, not a silver bullet. (That said, what is a silver bullet? Because I'd sure like one.)

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† Only applies to a project that has passed its initial rapid prototyping phase. During wild prototyping rides, types can indeed slow you down. But that's really the same debate as RDBMS vs NoSQL.