Why You Should Use Types Instead
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Types and In...
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IMO the described criteria are not enough to say “stop using” 😅 I’d say, use interfaces for object-oriented code and types for more functional codebases. And as usual, consistency importance prevails over specific choice.
My thoughts though 😃
STOP posting STOP posts if you are not aware of the topics you're ranting about. Interfaces and types have clear distinction on use cases and both are essential for TS.
💯
NO!
Interfaces are interfaces and type definitions are type definitions. You should probably dig into the history of both before starting another "best practices" scam.
Alternatively one could stick to what TypeScript team recommends. Always type over interface seems like religious fundamentalism 💁
"For the most part, you can choose based on personal preference, and TypeScript will tell you if it needs something to be the other kind of declaration. If you would like a heuristic, use interface until you need to use features from type."
STOP using CLICKBAIT titles
The argument that you should stop using interfaces because of declaration merging is completely bogus, since use of this typescript feature is extremely rare, and it's doubtful more than a few typescript programmers even know about it.
At Google we're required to use interfaces instead of types. If you do use a type, it gets flagged by the TS linter and the presubmit check would fail.
In practice types and interfaces are complimentary language features, and sometimes for advanced type manipulation, these features must be used in combination.
How do you handle generics that produce mapped types with mere interface if it's linter flagged? Do you just write new interface instead? 🤔
The rule at Google is, don't use a type if you can use an interface. Of course this doesn't rule out all use of type-style declarations. Really, it just boils down to this:
type T = {n: number};
vs
interface I {n: number}
The latter is allowed, the former is not.
I found out that the best for our team is to use types for data and interfaces for function parameters and vue component props.. This way we achieve both dependency inversion and interface segregation in our vue/ts cosebase.
eg.:
Function doesn’t and shouldn’t need to know anything about age.
The difference for us is simple. Type is always complete, interface might and probably is only partial.
That last line isn’t necessarily true. Types and interfaces both have support for optional parameters, and obviously at runtime it’s possible for any of the parameters to be undefined.
All you’re doing is inexplicitly creating an extended interface/intersection type.
I might missunderstood you, but my example is exactly the opposite I think.
It’s not about extending ‘Named’ with ‘age’ yet about ommiting ‘age’ from ‘Person’ without any direct dependency on it. So you can use ‘getFullName’ for types ‘Person’, ‘Cat’ or even a ‘Car’ as long as it satisfies ‘Named’ interface 🤔
Sure you can take it the other way and make your data be an intersection type of the component/function types it’s used at, but then there is no segregation..
Am I missing something?
Imagine being a "Person" but also being "Work"...
You'll soon be a "Person" implementing "Unemployed" if your employer sees this post!
Correction: According to my wife, I am indeed, a piece of "Work"...
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Thanks for the shout-out, but there is a lot that's incorrect in this article.
Classes can implement types.
Interface extensions are significantly faster for tsc to parse than intersections. Types and interfaces are the same, but the way you extend them matters.
There is no 'order of precedence' with declaration merging.
I still agree that types are preferred until you need a feature of interfaces, but I don't think this article has enough fact in it to be used as a reference.
Hello Matt 👏
Please do not write clickbait articles like this when you do not know what you are talking about. It is misleading for junior developers who do not know any better. To anyone reading the comments, ignore this article and instead follow the guidelines laid out by the Typescript team.
Tell me you know nothing about TypeScript without telling me you know nothing about TypeScript.
Interfaces are strict, types are not.
Tbh I feel like article does a better job of convincing you why you should use interfaces rather than shouldn’t.
The main drawback seems to be declaration merging and while that could cause issues, it’s pretty unlikely to happen in a well managed codebase, so I don’t think the argument is really strong enough.
For my projects I use interfaces primarily for defining object shapes, and then types for creating union types or extending existing types from libraries. They both have valid uses in most Typescript codebases.
Damn you got shut down… and rightly so
Especially, in large code bases, the performance of the interface is better than that of the type in some cases.
github.com/microsoft/TypeScript/wi...
I appreciate your efforts, but No thanks!
The title sounded clickbait, so i came for the comments to actually learn something.
Come work with me and I'll force you to use interface by default.
As both does almost the same, one should stick to what they are comfortable with.
Not informative at all or should I say it's misleading... It didn't give away any useful fact to prove we should not use Interfaces... Click Bait!
You didn't even justify the title of your artical. Please be carefully to select a title and stop wasting time of others.
Hmm your opinions. But I don’t think it’s a valid reason to say one should stop