app.fetch-httpClient.config.js

import {HttpClient} from 'aurelia-fetch-client'
import {Authentication} from './authentication';
import {BaseConfig} from './baseConfig'
import {inject} from 'aurelia-framework';
import {Storage} from './storage';

@inject(HttpClient, Authentication, Storage, BaseConfig)
export class FetchConfig {
    constructor(httpClient, authService, storage, config){
        this.httpClient = httpClient;
        this.auth = authService;
        this.storage = storage;
        this.config = config.current;
    }

    configure(){
        var auth = this.auth;
        var config = this.config;
        var storage = this.storage;
        var isConfigured = this.httpClient.isConfigured;

        this.httpClient.configure(httpConfig => {
          let defaults = {
            headers: {
              'Accept': 'application/json'
            }
          };
          let baseUrl = '';
          if (isConfigured) {
            if (Object.keys(this.httpClient.defaults).length > 0) {
              // respect user settings
              Object.assign(defaults, this.httpClient.defaults);
            }
            if (this.httpClient.baseUrl) {
              config.baseUrl = '';
              baseUrl = this.httpClient.baseUrl;
            }
          }
            httpConfig
            .withBaseUrl(baseUrl)
            .withDefaults(defaults)
            .withInterceptor({
                request(request) {
                    if (auth.isAuthenticated() && config.httpInterceptor) {
                        var tokenName = config.tokenPrefix ? `${config.tokenPrefix}_${config.tokenName}` : config.tokenName;
                        var token = storage.get(tokenName);

                        if (config.authHeader && config.authToken) {
                            token = `${config.authToken} ${token}`;
                        }

                        request.headers.append(config.authHeader, token);
                    }

                    return request;
                }
            });
        })
    }
}