What is a generic function in TS

1. way to write code that is Type flexible without using “any”

function genericFunction<T>(arg: T) {
		return "string" as T
}

what is “as const” in TS and diff bw this and normal “const”

1. allows us to write objects that are sealed in a way that you cannot modify any part of the object, ex. DB config
2. TS is a developer tool → everything applies during build time
3. JS Object.freeze applies at runtime and only at first level → does not apply to nested data

const config = { 
		host: "123",
		port: 45
}
// can be modified
config.host = "456"

const config = { 
		host: "123",
		port: 45,
		auth: {
				client: "abc"
		}
} as const; // nested fields and objects are immutable now

what does the private access modifier do when added to a class

1. private → cannot be accessed outside of class → interface segregation

TS decorator, what is it and what is the use case

1. way to reuse code following decorator pattern
2. class inheritance → violates liskov substitution → creates messy chain

// apply code to multiple classes
function Injectable(){}

@Injectable
class Service {...}

difference bw type vs. interface

1. at build time interfaces are merged
2. types have to be unique → duplicate types will give type error
3. request type - interface - extend - props/auxiliary
4. type - define domain entities

type guard

1. constraints added to filter types

structural vs nominal typing

1. TS → structural typing - if 2 objects have the same properties then they are the same - interchangeable - gives flexibility to combine and interchange objects if they satisfy the same properties
2. Java/C# → nominal typing - objects must match same signature to be the same, have to be instances of the same class