token.interceptor.ts

import { Injectable } from '@angular/core';
import {
  HttpRequest,
  HttpHandler,
  HttpEvent,
  HttpInterceptor
} from '@angular/common/http';
import { Observable } from 'rxjs';
import { NbAuthOAuth2Token, NbAuthService } from '@nebular/auth';

@Injectable()
export class TokenInterceptor implements HttpInterceptor {

  token;
  constructor(public auth: NbAuthService) { }

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    if (req.url.indexOf('/assets/') > -1) {
      return next.handle(req);
    }

    if (req.url.indexOf('/oauth2/token') > -1) {
      return next.handle(req);
    }

    this.auth.getToken().subscribe((x: NbAuthOAuth2Token) => this.token = x);
    let newHeaders = req.headers;
    if (this.token.getPayload() != null) {
      newHeaders = newHeaders.append('Authorization', 'Bearer ' + this.token.getPayload().access_token);
    }
    const authReq = req.clone({ headers: newHeaders });
    return next.handle(authReq);
  }
}