import { Injectable } from '@angular/core';
import { RequestOptions } from '@angular/http';

@Injectable()

export class SharedService {
headers;
url = 'http://localhost:8000/api/';

constructor() {
    this.headers = '';
}

setHead(token: string){
    this.headers = new Headers({
        'Authorization': 'Bearer ' + token,
        'Content-Type': 'application/json'
    });
}

getHead(){
    return new RequestOptions({ headers: this.headers });
}

}

import { SharedService } from './shared.service';

@NgModule({
bootstrap: [AppComponent],
providers: [
    ...
    SharedService,
],
export class AppModule {
}

constructor(
    private authService: NbAuthService,
    private sharedService: SharedService
) {
    this.authService.onTokenChange()
    .subscribe((token: NbAuthJWTToken) => {
        if(token.isValid()){
            this.sharedService.setHead(token.toString());
        }
    });
}

body : null
headers : Headers
    __proto__ : Headers
method : null
params : undefined
responseType : null
search : (...)
url : null
withCredentials : null
__proto__ : Object