Fetch.js

fetch.js

var fetch = function (url) {

  return new Promise(function (resolve, reject) {
  
    var xhr = new XMLHttpRequest();
    xhr.open('GET', url);
    xhr.onload = function() {
  
      if (xhr.status === 200) {
        resolve(xhr);
      } else {
        reject(xhr.status);
      }
    };
    xhr.send();
  });
};

/* Usage */

fetch('/')
  .then(function (body) { return body.responseText; })
  .then(function (str) { console.log(str); })
  .catch(function (err) { console.log(err); });
  
/* With ES7 async/await */
(async function() {
  var users = await fetch('/users');
  var user = await fetch('/users/' + users[0].id);
  console.log(user);
})();