Network Interceptor for Offline Redirect (Angular)

network.interceptor.ts

import { Injectable } from '@angular/core';
import {
    HttpRequest,
    HttpResponse,
    HttpHandler,
    HttpEvent,
    HttpInterceptor
} from '@angular/common/http';
import { Router } from '@angular/router';

// RXJS
import { Observable } from 'rxjs/Observable';
import { map } from 'rxjs/operators';


@Injectable()
export class NetworkInterceptor implements HttpInterceptor {
    constructor(private _router: Router) { }

    intercept<T>(req: HttpRequest<T>, next: HttpHandler): Observable<HttpEvent<T>> {
        return next.handle(req).pipe(
            map((event: HttpEvent<any>) => {
                let onLine = navigator.onLine;

                if (!onLine) {
                    this._router.navigate(['/offline']);
                }

                if (event instanceof HttpResponse) {
                    if (event.status === 524) {
                        this._router.navigate(['/offline']);
                    }
                }

                return event;
            }));
    }
}