No 'Access-Control-Allow-Origin' header is present on the requested resource

window.onload = function() {
	var mb = document.getElementById("myBtn");
	mb.addEventListener("click", clickSomethingMatch);
}
function clickSomethingMatch() {

	var createCORSRequest = function(method, url) {
	  var xhr = new XMLHttpRequest();
	  if ("withCredentials" in xhr) {
	    // Most browsers.
	    xhr.open(method, url, true);
	  } else if (typeof XDomainRequest != "undefined") {
	    // IE8 & IE9
	    xhr = new XDomainRequest();
	    xhr.open(method, url);
	  } else {
	    // CORS not supported.
	    xhr = null;
	  }
	  return xhr;
	};

	var url = 'https://euw1.api.riotgames.com/lol/summoner/v3/summoners/by-name/NAMEXXX?api_key=APIKEYXXX';
	var method = 'GET';
	var xhr = createCORSRequest(method, url);
	xhr.send();

	xhr.onerror = function() {
		alert('Woops, hay un error con el request');
	}
	xhr.onreadystatechange =  function(a) {
	  if (xhr.readyState == 4 && xhr.status == 200) {
			var response = JSON.parse(xhr.responseText);
		}
		document.getElementById("span").innerText = response;
	};
}