ajax helper

ajax-helper.js

function ajax (opts) {
  if (this instanceof ajax) throw new Error("stop instantiating me!");
  if (!opts) throw new Error("pass opts, dummy.")
  if (!opts.url) throw new Error("pass url, dummy");
  if (!opts.method) throw new Error("pass method, dummy");

  var callbacks = {
    success: [],
    failure: [],
    always: []
  };

  var ret = Object.keys(callbacks).reduce(function(obj, key) {
    obj[key] = function (cb) { callbacks[key].push(cb); return ret; };
    return obj;
  }, {});

  var req = new XMLHttpRequest();
  req.open(opts.method.toUpperCase(), opts.url);
  req.onreadystatechange = function () {
    if (!(req.readyState === 4)) { return; }
    var ok = req.status >= 200 && req.status < 400;
    var fns = callbacks[ok ? "success" : "failure"];
    fns.forEach(function (cb) { cb(req); });
    callbacks.always.forEach(function (cb) {cb(req); });
  };
  req.send(opts.data);

  return ret;
}