src/deps/ajax/prequest-browser.js

import ajaxCore from './ajaxCore';

function ajax(opts, callback) {

  // cache-buster, specifically designed to work around IE's aggressive caching
  // see http://www.dashbay.com/2011/05/internet-explorer-caches-ajax/
  // Also Safari caches POSTs, so we need to cache-bust those too.
  var ua = (navigator && navigator.userAgent) ?
    navigator.userAgent.toLowerCase() : '';

  var isSafari = ua.indexOf('safari') !== -1 && ua.indexOf('chrome') === -1;
  var isIE = ua.indexOf('msie') !== -1;

  var shouldCacheBust = (isSafari && opts.method === 'POST') ||
    (isIE && opts.method === 'GET');

  var cache = 'cache' in opts ? opts.cache : true;

  if (shouldCacheBust || !cache) {
    var hasArgs = opts.url.indexOf('?') !== -1;
    opts.url += (hasArgs ? '&' : '?') + '_nonce=' + Date.now();
  }

  return ajaxCore(opts, callback);
}

export default ajax;