TypeScript at Google

Post by evmar » Sun, Sep 02, 2018, 3:01 PM UTC

MBCook wrote: post #128

cribbles wrote: post #109

> Gmail engineers had to worry so much about Internet Explorer's poor garbage collection algorithm that they'd need to manually hoist string literals out of for loops to avoid GC pauses. What does this mean in practice? I know about variable hoisting and function scoping, but not about old JS GC algos.

My read was that Internet Explorer couldn’t realize that a string variable could be reused over and over so each iteration of the loop it was allocating a new one, using it, and then garbage collecting it. Basically tons of unnecessary overhead. Having the programmer define a variable before the loop and then reuse it each iteration meant that all that allocation and garbage collection wasn’t necessary during the pas…

Post by bcherny » Sun, Sep 02, 2018, 3:09 PM UTC

wwwigham wrote: post #92

bcherny wrote: post #48

Earlier quoted context omitted.

Hey, that’s an interesting thought! If you go all the way and make it sound with variance annotations, banning asserts & under specified types, etc. then you end up with a language that sucks to use in practice. If you go to the other extreme, you don’t have static types at all. If different parts of your code are typed to varying degrees, or you use a lot of unsound types/inferences, maybe there’s a way to assign a…

> If you go all the way and make it sound with variance annotations Variance annotations aren't quite what would make the language (in strict mode) sound. Specifically, what makes it unsound is the `any` type (generally) and the lack of enforced variance on methods, non-function properties, and index signatures. It doesn't need annotations to determine variance - type parameter variance can be inferred from where in…

Post by evmar » Sun, Sep 02, 2018, 3:11 PM UTC

wwwigham wrote: post #92

bcherny wrote: post #48

Earlier quoted context omitted.

Hey, that’s an interesting thought! If you go all the way and make it sound with variance annotations, banning asserts & under specified types, etc. then you end up with a language that sucks to use in practice. If you go to the other extreme, you don’t have static types at all. If different parts of your code are typed to varying degrees, or you use a lot of unsound types/inferences, maybe there’s a way to assign a…

> If you go all the way and make it sound with variance annotations Variance annotations aren't quite what would make the language (in strict mode) sound. Specifically, what makes it unsound is the `any` type (generally) and the lack of enforced variance on methods, non-function properties, and index signatures. It doesn't need annotations to determine variance - type parameter variance can be inferred from where in…

Post by 52-6F-62 » Sun, Sep 02, 2018, 3:27 PM UTC

sandGorgon wrote: post #98

nojvek wrote: post #51

Earlier quoted context omitted.

Typescript will happily check your JavaScript code with “allowJs” compiler flag. We write all our new code in good ol ES6 flavor of JavaScript and typehint in jsdoc. Typescript as a typechecker serves as very well. It’s a great incremental adoption strategy.

can you explain how this works ? this is very interesting to us. We have a large react app (created using create-react-app) in ES6 and have been considering adopting TS gradually. This seems a great first step.

    {
        “compilerOptions”: {
            “allowJs”: true,
            “esModuleInterop”: true
        },
        “include”: [ “src/**/*” ],
        “exclude”: [ “node_modules/**/*” ]
    }

Post by nojvek » Sun, Sep 02, 2018, 3:30 PM UTC

alangpierce wrote: post #59

nojvek wrote: post #49

Earlier quoted context omitted.

Typescript compiler architecture is quite different to flows. Typescript was written from the get go to provide really fast and accurate intellisense to IDEs. The newer refactoring powers are super nice too. Most ides just ask typescripts language service “hey, my user’s cursor is here, what should I show for code completion?” I think that’s what differentiates TS from flow. Typescript thought about the whole develop…

To Flow's credit, their language server does provide IDE features: https://github.com/flowtype/flow-language-server#supported-f... I still have found TypeScript to be an overall more pleasant developer experience, though.