Conditional Types - Advanced TypeScript

A conditional type (T extends U ? X : Y) in TypeScript selects one of two possible types based on some condition.

👨‍🏫 Take a QUIZ to solidify the information you've got from this video:

Table of Contents:
00:05 Conditional type definition
00:55 A basic example
01:57 Deferred evaluation of a conditional type
05:22 Nested expression
06:19 Distributive conditional types and using a conditional type with the "never" type for filtering union types
11:40 When a conditional type is not distributive
15:38 Type inference in conditional types
22:36 Other utility types which use a conditional type

👨‍💻 My Udemy Course:
Using TypeScript with React

[billmcbungabine]

I've been searching for more advanced lessons covering typescript for a while and these are by far the best i've found and they are explained very well especially considering by the sounds of it English is not your native language - well done hope you release more content like this

[dawid_dahl]

Thanks so much for providing more advanced TS content for free.

[pjeet]

This is great tutorial on advanced Typescript.

I had pause in every 10mins to understand different type of format the extends take like type comparison, function comparison and tuple comparison.

[burnCS]

One of the best tutorials about conditional types. Can't wait for more videos :)

[v]

Hi, Dmytro! Thanks for sharing the knowledge on a more advanced topic.

[bradyfractal]

Your channel is a gold mine!! You’re a very talented teacher 💙

[孙凌峰-wb]

15:04 what is different between 'type StringNot<T> = T extends 'a'|'b' ? T :never' and 'type MyStringNot<T> = [T] extends ['a'|'b'] ? T :never' . I still don't understand .

[nazaka]

Дякую за туторіал. Добре описана теорія, але хотілося б більше прикладів прикладного використання

[jacinyan]

Just started learning TS, and I have been confused about the ‘extends’ keyword in here with say, interface/classes. Now it is kinda explained

[RachidBoukotos]

thank you very much, it's really informative

[darkknight]

Wow! Amazing tutorial ❤ . Thanks for sharing your understanding it greatly appreciated.

[harini]

Can u make more videos on typescript like this?, thanks

[dimitargetsov]

Dear Sir, at 22.44:
type ReturnType<T extends(...args:any)=>any>=T extends(...args:any)=>infer R?R:any;
should be, IMAO, :
type ReturnType<T>=T extends(...args:any)=>infer R?R:any;
Do You need (and why) to write that generic type T <T extends (...args:any)=>any>
in the parameter list of ReturnType?
Best regards.

[codewithnws]

hey can you please create the video for infer?

[Borisua]

Good stuff, but what about practical use chases?

[sourishdutta]

You are too good :) make more videos like this

[bakaleisanich]

Будут ли курсы по базовому тайпскрипт?

[ankitshukla]

I have an interface defined as
interface Xyz {
abc?: string;
}
I do not know what ?: means here. Can anyone help?

[adiscivgin]

Hi all, if someone may help I would appreciate it. I have this interface:
export interface StorageModuleConfig {
appName: string;
perUser?: boolean;
authPrefixKey?: string;
}
My task is to make authPrefixKey required only and only if user provide value for perUser property.

[olga-angel]

Для чого робити відеоуроки англійською, коли їх і так океан... Робіть українською, своє українське море.