fetch.js

import 'isomorphic-fetch';

const getOkAndJsonBody = res => {
  return res.text().then(text => {
    try {
      return {ok:res.ok,body: text && JSON.parse(text) || {}};
    } catch (err) {
      return {ok:res.ok,body:{}};
    }
  });
};

const checkOk    = res => res.ok ? res : Promise.reject(res);
const unwrapBody = res => res.body;

export const fetchJson = (url, options = {}, overrideMethod) => {
  if (overrideMethod) options.method = overrideMethod;
  if (!options.headers) options.headers = {};
  options.credentials = 'same-origin';
  options.headers['Accept'] = 'application/json';
  if (options.body) {
    options.headers['Content-Type'] = 'application/json';
    if (typeof options.body !== 'string') {
      options.body = JSON.stringify(options.body);
    }
  }
  return fetch(url, options)
    .then(getOkAndJsonBody)
    .then(checkOk)
    .then(unwrapBody);
};

export const getJson    = (url, options) => fetchJson(url, options, 'GET');
export const postJson   = (url, options) => fetchJson(url, options, 'POST');
export const putJson    = (url, options) => fetchJson(url, options, 'PUT');
export const deleteJson = (url, options) => fetchJson(url, options, 'DELETE');