What is the mechanism behind Typescript interface scope? How can interfaces be defined globally in Typescript?

Question

What is the mechanism behind Typescript interface scope? How can interfaces be defined globally in Typescript?

I'm diving into the world of Typescript and Deno, but I'm struggling to understand how interfaces scopes work.

Here's the structure of my application:

The first layer (App.ts) contains the core logic of my application. This layer can reference the second layer (API.ts).

The second layer (API.ts) serves as the entry point for communication with external APIs like Facebook, Stripe, and Google API.

The third layer consists of multiple .ts files, each handling a specific part of an API. For example, FB_page.ts manages interactions with the Facebook pages API, while STRP_Subscription.ts is responsible for handling subscriptions in the Stripe API.

My issue lies in managing numerous interfaces that define parameter types, errors, and responses for API calls. These interfaces need to be accessible across all layers of my application.

It would be ideal to place interfaces related to a particular API within the file handling that API. For instance, having Facebook page API interfaces inside FB_page.ts.

However, constantly importing these interfaces across different layers, like in App.ts, using

import {IPost, IPost_Error, IPost_Response} from '../lib/FB_page.ts';

is cumbersome.

I initially stored these interfaces in .d.ts files, but they don't seem to be globally available either. How can I make my interfaces accessible without the need for repetitive imports throughout my application?

Thank you for your guidance.

typescript deno

Answer 1

Answer №1

In Deno, the majority of components are treated as modules. If you supply a non-module or script that contains global types, it may not be detected by Deno. Additionally, Deno does not handle files with a .d.ts extension well, except in specific cases where compiler hints are utilized.

How to Address this Issue

Change the file extensions of the interfaces to .ts.
Place global types within a module (a file containing import/export statements).
Ensure the module is imported, so that Deno CLI can locate it during compilation.

It's important to note that Deno employs its own integrated TypeScript compiler, which differs from the one used by your IDE (such as VS Code). Therefore, lack of type errors displayed in your IDE does not guarantee successful compilation using deno run or deno cache commands.

Sample Code Illustration

// Insert the following code snippet into one of your utilized modules
declare global {
  interface IPost {
    foo: string;
  }
}

// IPost will be accessible globally without requiring an import statement
const post: IPost = { foo: "bar" };

If you wish to separate the global types from the rest of your code, you can employ a side-effect import:

import "./lib/global.ts";
const post: IPost = { foo: "bar" };

global.ts:

export {}; // utilize some form of export to designate the file as a module
declare global {
  interface IPost {
    foo: string;
  }
}

Answer 2

In Deno, the majority of components are treated as modules. If you supply a non-module or script that contains global types, it may not be detected by Deno. Additionally, Deno does not handle files with a .d.ts extension well, except in specific cases where compiler hints are utilized.

How to Address this Issue

Change the file extensions of the interfaces to .ts.
Place global types within a module (a file containing import/export statements).
Ensure the module is imported, so that Deno CLI can locate it during compilation.

It's important to note that Deno employs its own integrated TypeScript compiler, which differs from the one used by your IDE (such as VS Code). Therefore, lack of type errors displayed in your IDE does not guarantee successful compilation using deno run or deno cache commands.

Sample Code Illustration

// Insert the following code snippet into one of your utilized modules
declare global {
  interface IPost {
    foo: string;
  }
}

// IPost will be accessible globally without requiring an import statement
const post: IPost = { foo: "bar" };

If you wish to separate the global types from the rest of your code, you can employ a side-effect import:

import "./lib/global.ts";
const post: IPost = { foo: "bar" };

global.ts:

export {}; // utilize some form of export to designate the file as a module
declare global {
  interface IPost {
    foo: string;
  }
}

Answer 3

Answer №2

Consider utilizing namespace exports

export as namespace EventCalendar;
import { Document } from "mongoose";

export interface CalendarEvent extends Document {
attendeeId?: Object
}

Answer 4

Consider utilizing namespace exports

export as namespace EventCalendar;
import { Document } from "mongoose";

export interface CalendarEvent extends Document {
attendeeId?: Object
}

What is the mechanism behind Typescript interface scope? How can interfaces be defined globally in Typescript?

Answer №1

How to Address this Issue

Sample Code Illustration

Answer №2

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