My snippets

download.js

/**
 * file download in current page.
 * @param {String} selector CSS selector
 * @param {HTMLElement} [target] element which does not belong document root
 * @example download('img')
 */
function download(selector, target) {
    target = target instanceof HTMLElement ? target : document;
    var elements = target.querySelectorAll(selector);
    for (var i = 0, anchor, evt; i < elements.length; i++) {
      evt = document.createEvent('MouseEvents');
      evt.initMouseEvent('click', false, false, window, 0, 0, 0, 0, 0, false, true, false, false, 0, null);
      anchor = document.createElement('a');
      anchor.href = elements[i].href || elements[i].src;
      anchor.dispatchEvent(evt);
    }
}

request.js

(function() {
// ifdef request
if (typeof window.request !== 'undefined') {
  throw new Error('defined request.');
}
// define request
window.request = Request;
// class
function Request() {

}
Request.get = function(url, object) {
  // send request
  var request = new XMLHttpRequest();
  request.open("GET", url+'?'+createParameter(object).substr(1), false);
  request.send();

  return request.responseText;
};
Request.post = function(url, object, callback) {
  var request = new XMLHttpRequest();
  request.open("POST", url, false);
  request.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
  request.send( createParameter(object).substr(1) );

  return request.responseText;
};

// private function
function createParameter(object) {
  var param = '';
  for (key in object) {
    if (!object.hasOwnProperty(key) || typeof object[key] === 'function') continue;
    param += '&'+key+'='+encodeURIComponent(object[key]||'');
  }
  return param;
}


})();