CORS-Enabled XHR with Feature Detection
// Script running on http://www.contoso.com var xhr = new XMLHttpRequest(); if ("withCredentials" in xhr) { xhr.onerror = _handleError; xhr.onload = _handleLoad; xhr.open("GET", "http://photos.contoso.com/albums", true); xhr.send(); } else { // Fallback behavior for browsers without CORS for XHR }
XHRでCORSを行えるかどうかの判定
via. IEBLOG (http://blogs.msdn.com/b/ie/archive/2012/02/09/cors-for-xhr-in-ie10.aspx)