What exactly does ".default" signify in Angular, Typescript, or Javascript?

Could someone please clarify the significance of the ".default" in the code snippet below?

I am interested in implementing this code in our project, but my understanding of the mentioned code fragment is uncertain.

(I have modified my question to display the original code.)

In the article angular-http-mock-interceptor-for-mocked-backend-1h5g on dev.io, there is code that looks like this:

import { Injectable, Injector } from '@angular/core';
import { HttpEvent, HttpHandler, HttpInterceptor, HttpRequest, HttpResponse } from '@angular/common/http';
import { Observable, of } from 'rxjs';
import * as users from './users.json';

const urls = [
    {
        url: 'https://an-example.url.org/users',
        json: users
    }
];

@Injectable()
export class HttpMockRequestInterceptor implements HttpInterceptor {
    constructor(private injector: Injector) {}

    intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        for (const element of urls) {
            if (request.url === element.url) {
                return of(new HttpResponse({ status: 200, body: ((element.json) as any).default })); // <---- THIS ".default"
            }
        }
    //...
    }
}

with users.json

[
 {
   "name": "Abe",
   "id": 1
 },
 {
   "name": "Boe",
   "id": 22
 }
]

I have attempted to search for an explanation online without success. I am unsure if it is safe to proceed without including the ".default" in the code, perhaps I am overlooking something. I would greatly appreciate any insight into its meaning. Thank you.

Answer №1

The rationale behind the default setting is due to the star import used here

import * as users from './users.json';

An alternative approach would be to adjust the import statement to

import users from './users.json';

Changing the import will result in a code break, thus requiring the removal of the default and modifying the line to

return of(new HttpResponse({ status: 200, body: element.json }));

https://i.sstatic.net/p8twK.png

The reason for the necessity of casting it is because json.element does not contain that default property.

The preceding image merely displays a console.log of the const urls.

The following is the StackBlitz URL. https://stackblitz.com/edit/angular-mock-http-interceptor?file=src%2Fapp%2Finterceptor.mock.ts

I am perplexed by the sequence. It is initially "cast" to any, and then the default property is accessed. This aspect puzzles me.

A more intuitive approach might be to assign the url type to any, which does prove to be effective.

const urls:any = [
    {
        url: 'https://jsonplaceholder.typicode.com/users',
        json: users
    }
];

@Injectable()
export class HttpMockRequestInterceptor implements HttpInterceptor {
    constructor(private injector: Injector) {}

    intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        for (const element of urls) {
            if (request.url === element.url) {
                console.log('Loaded from json : ' + request.url);
                return of(new HttpResponse({ status: 200, body: element.json.default }));
            }
        }
        console.log('Loaded from http call :' + request.url);
        return next.handle(request);
    }
}

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