super simple implementation of getJSON

getjson.js

function getJSON(url, cb) {
  var xhr = new XMLHttpRequest();
  xhr.open("GET", url, true);
  xhr.onreadystatechange = function() {
    if (xhr.status != 200 || xhr.readyState != 4) return;
    cb(JSON.parse(xhr.responseText));
  }
  xhr.send();
};

getjsonp.js

function getJSONP(url, cb_name, cb) {
  var existing_cb = window[cb_name] || function(){};
  window[cb_name] = function() {
    try {
      cb.apply(this, arguments);
    } catch(err) {}
    existing_cb.apply(this, arguments);
  }
  var script = document.createElement("script");
  script.type = "text/javascript";
  script.src = url;
  document.body.appendChild(script);
}