digitransit-ui/app/util/xhrPromise.js

function serialize(obj, prefix) {
  if (!obj) {
    return '';
  }

  return Object.keys(obj)
    .map(p => {
      const k = prefix || p;
      const v = obj[p];

      return typeof v === 'object'
        ? serialize(v, k)
        : `${encodeURIComponent(k)}=${encodeURIComponent(v)}`;
    })
    .join('&');
}

// Return Promise for a url json get request
export function getJson(url, params) {
  return fetch(
    encodeURI(url) +
      (params ? (url.search(/\?/) === -1 ? '?' : '&') + serialize(params) : ''),
    {
      timeout: 10000,
      method: 'GET',

      headers: {
        Accept: 'application/json',
      },
    },
  ).then(res => res.json());
}

// Return Promise for a json post request
export function postJson(url, params, payload) {
  return fetch(
    encodeURI(url) +
      (params ? (url.search(/\?/) === -1 ? '?' : '&') + serialize(params) : ''),
    {
      timeout: 10000,
      method: 'POST',
      body: payload,

      headers: {
        Accept: 'application/json',
        'Content-Type': 'application/json',
      },
    },
  ).then(res => res.json());
}

// Return Promise for array of json get requests
export function getJsons(urls) {
  return Promise.all(urls.map(url => getJson(url)));
}