Example abstract fetch

api.js

/**
 * Created by @johnwmcarneiro 30/04/2019
 * 
 * Requires:
 * - querystring
 */
'use strict';

const { stringify } = require('querystring');

import { PROD_BASE_URL, DEV_BASE_URL } from './env.config';

let baseURL = PROD_BASE_URL;
if (__DEV__) {
  baseURL = DEV_BASE_URL;
}

export const BASE_URL = baseURL + '/api/v1';

export default class Api {
  static userToken = null;

  static setUserToken(token) {
    this.userToken = token;
  }

  static resetUserToken() {
    this.userToken = null;
  }

  static async request(endpoint, customOptions = {}) {
    const standardOptions = {
      method: "GET",
      requireAuth: true,
      data: {},
      headers: {}
    };

    let options = Object.assign({}, standardOptions, customOptions);

    let headers = new Headers(Object.assign({}, {
      Accept: "application/json",
      "Content-Type": "application/json"
    }, options.headers));

    if (options.requireAuth) {
      headers.set("X-User-Token", this.userToken);
    }

    let uri = BASE_URL + endpoint;
    let method = options.method;
    let data = options.data;
    let fetchOptions = { method: method, headers: headers };

    if (method === "GET" || method === "DELETE") {
      uri += "?" + stringify(data);
    } else {
      if (data instanceof FormData) {
        fetchOptions.body = data;
      } else {
        fetchOptions.body =  JSON.stringify(data);
      }
    }

    if (__DEV__) {
      console.info(`Call api: ${uri} with options ${JSON.stringify(fetchOptions)}`);
    }

    let response = await fetch(uri, fetchOptions);

    try {
      return await response.json();
    } catch (e) {
      return {};
    }
  }
}

env.config.js

export const PROD_BASE_URL = 'http://api.production.com';
export const DEV_BASE_URL = 'http://192.168.0.1:3000';

example.js

import Api from 'api';

Api.setToken('TOKEN');

Api.request('/posts'); // GET
Api.request('/posts', { method: 'POST', data: { name: 'John' } }); // POST
Api.request('/posts', { method: 'PUT', data: { name: 'John' } }); // PUT

// With FormData
let data = new FormData();
data.append('name', 'John');
data.append('emails[]', 'johnwmcarneiro@gmail.com');
data.append('emails[]', 'contato@capapreta.com.br');
Api.request('/users', { method: 'POST', data: data });