I am experimenting with typescript in the typescript playground and found that it allows me to assign the object returned by JSON.parse() to a class, even though the object won’t have any methods, and this causes a runtime error. This is surprising to me as my understanding was that typescript is typesafe as long as you don’t use as or Any.

I am using nop function that gives correct typing for a Record-like structure for auto completion purposes that looks like this:

I am working on a TypeScript solution to ensure exhaustive type-checking for dynamic form fields. The goal is to make sure that all required fields defined in an interface are included in the form configuration (I’m 90% there). While the first example works as expected, the second example should throw a type error because it is missing a required field, but no error is thrown. Here is a TsPlay link or my code below

Is it possible to infer the type of a second argument, which is a callback in my case, based on the enum value of the first argument.

Let’s say I have a type to denote a language code, for example:

I have type:
type Primitive = number | string | boolean | object | symbol;
and a function which I want to be sure gets objects which have all properties of type Primitive | undefined or Primitive[] but which can’t have properties of type Primitive or undefined or null etc.
I tried type OptionalPrimitive = (number | undefined) | (string | undefined) | (boolean | undefined) | (object | undefined) | (symbol | undefined);
and later using it in mapped type:
[key: string]: OptionalPrimitive | Primitive[]; but it doesn’t work

I have a TypeScript function subscribe that is used to subscribe to specific event types extracted from a union type. The function definition and type declarations are as follows:

In Typescript, all of these 3 types are similar, in that they are only made of primitive types, maps and arrays:

type Has2<T extends readonly any[], U> = T[number] extends U ? true : never; type UU = [‘Kars’, ‘Esidisi’]; type AA = Has2<UU, ‘Kars’>; I think AA should be type true, but type is never I don`t know why i try to ask chatGPT but it`s answer is that type AA is true typescript types […]