Most TS devs don't understand 'satisfies'

00:00 Intro
00:33 Variable annotations
00:53 What satisfies does
02:01 When satisfies is GOOD
02:39 When variable annotations are BAD
03:41 Outro

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[nazaka]

I wish you added that 'satisfies' can be combined with 'as const'. It is obvious, but still nice to mention i think

[liornz]

You have made such an impact on the TS community, and enriched us all with your courses, articles and YouTube content. Thank you so much!! I wish us all a wonderful new TypeScript year 🎉

[dechobarca]

This video satisfies any TypeScript developer. Thumbs up for you Matt.

[nbb]

Before "satisfies" you had to make a choice whether you want something to adhere to a type OR be of the more specific type. With "satisfies" you get both.

[EngineerNick]

oh man thankyou I have been looking for this functionality/keyword for like an hour now. So hard to search for if you dont know what it is called. knew I would find it here! I was so sure that the `as` keyword was not the end of the line.

[ibgib]

`satisfies Partial<MyInterface>` phenomenally useful

[ShivKumar-qgmt]

You don't know how much you helped me with this. I didn't know about this `satisfies` keyword and I had to write duplicate code to get object constraint with autocompletion as typing out `Record<string, T>` on variable I always loose keys autocompletion.

[Dev-Siri]

typing a word like "satisfies" is satisfying

[JacobDrebin]

Thanks for this explanation! In essence, this is like writing:
const name: extends string = "sam";
Which is something I've always wanted to be able to do.

[budivoogt]

Great explanation Matt! Thanks. Will try to narrow my types further where possible to get more autocompletion.

[edgeeffect]

Seems like ages since you last popped up in my feed and said "what's up wizards".... welcome back. :)

[mikael.sevigny]

Fantastic content once more, thanks Matt! I appreciate the single-topic video format as well. I'm also looking forward to the book release, especially since the premium TT courses are a bit too expensive for me to purchase at the moment.

[SudeeptoDutta]

Thank you for this clear explanation. Please continue making such videos focusing on a specific topic only.

[PaulSebastianM]

Takeaway 1: satisfies is a static typing mechanism for literal values (things that are created and assigned inline after an equals sign).

[BoudewijnDanser]

All the best for 2024 Matt, hope you keep making awesome content for all the wizards!

[anj]

How `as const` plays into this? When to use one over the other or both at the same time?

[jonathanadamsson]

I found it useful sometimes when asserting string literals, say I have something like `type State = 'Idle' | 'Succes' | 'Error'`, then in another place in the code I might have `'Idle' satisfies State`, which will assure the type error is caught if I ever change the string literal

There are better ways to handle this typically but in some situations it can be pretty useful

[xbsidesx]

I started using satisfies more because of its “const” value as well. This is such a good tip. Awesome video as always!

[cool_scatter]

I would have loved you to show off satisfies's power a little more at the end by showing one of those massive config objects! It can get really useful when combined with discriminated unions for different types of config options as well

[Cahnisama]

This video has been very satisfying, thanks Matt