Advertisements I have a JavaScript class that extends the instance with constructor options: class C { constructor(options) { Object.assign(this, options) } } That means that the class instance is going to have all of the properties of the options object. I’m looking for a way to write a .d.ts definition for that class without duplicating… Read More Include an interface into a class in a .d.ts file

Advertisements For example, I have this code: interface DbType { id: string, } interface RowType extends DbType { name: string } class db<T> { // How do I put that it must be an extension of DbType? insert(item: T) { } delete(id: [typeof id]) { } // What should I put here? } I want… Read More How to assign same type as one of the type member?

Advertisements I’m trying to implement a UI where a client can search using either of many attributes. AFAIK this could be achieved with union types. So far my implementation looks like this interface GivenNameSearchTerm { readonly givenName: string; } interface FamilyNameSearchTerm { readonly familyName: string; } type SearchTerm = GivenNameSearchTerm | FamilyNameSearchTerm; const search =… Read More Key of union type as function argument

Advertisements I have 2 sets of keys: KEY_SET_1 and KEY_SET_2. KEY_SET_1 has keys A to D while KEY_SET_2 has keys E to H. I have a function that needs to handle key in both key sets differently. However, I run into an error that says Argument of type ‘AllKeySetType’ is not assignable to parameter of… Read More How to resolve "Type is not assignable to type" in TypeScript if statement?

Advertisements Angular Material’s documentation says: import { MatSlideToggleModule } from ‘@angular/material/slide-toggle’; @NgModule ({ imports: [ MatSlideToggleModule, ] }) class AppModule {} But Angular 17 doesn’t create app.module file by default. Is there any way to do that without app.module? >Solution : Angular v17 onwards, standalone is default via CLI Which means when you create new… Read More How to include Angular Material in Angular 17?

Advertisements type JsonType<T> = { [P in keyof T as Exclude<P, "salt" | "hash">]: string; }; type Test = { salt: string; hash: string; }; const testObject: JsonType<Test> = { hash: "…", salt: "…", }; why I’m not getting any error for defining an object named testObject of type JsonType<Test>? I excluded "salt" and "hash"… Read More Why doesn't TypeScript produce an error for this mapped type?

Advertisements It it possible to have a getter property in TypeScript that replaces itself with an instance property. I have a class with lots of metadata properties and most instances wont call them so I only want to create an instance if they are needed but I also don’t want to be calling a property… Read More Self instantiating properties in TypeScript

Advertisements At first, I’d like to reproduce my issue. Create a new Angular project ng new ng-ts-strict-issue cd ng-ts-strict-issue Modify compilerOptions in tsconfig.json. Let’s set strict to false. { … "compilerOptions": { … "strict": false, … }, … } Add a method to the app.component.ts. test(p: string): string | null | undefined { if (p… Read More The "error TS7030: Not all code paths return a value." caused by "strict": false in tsconfig.json

Advertisements I had the following code using signals which I implemented with Angular 16.x: protected errors = signal<string[]>([]); @Input() set error(error: string) { if (error) { if (this.errors().indexOf(error) === -1) { this.errors.mutate((errors: any) => errors.push(error)); } } else { this.errors.set([]); } } After upgrading the version to Angular 17.x, I trying to run the unit… Read More How to fix Property mutate does not exist on type WritableSignal<string[]>

Advertisements I have a union type whose elements have a discriminator property called "type". I then declare a Record<> whose keys are the "type" property values. How do I declare the Record’s second generic parameter (Record< , this param>) such that values in the map/record are inferred based on the corresponding key? TypeScript Playground interface… Read More How to narrow discriminated union based on Record key value