I have a programm in React that

does a http-request during componentWillMount and sets a variable response on the response of the http-request

var response = "";
class App extends Component{
  componentWillMount(){
     var myRequest = new XMLHttpRequest(),
        method = 'GET',
        url = //url; 
      myRequest.open(method, url, true);
      myRequest.send();
      myRequest.onload = function() {
        response = myRequest.response;
    };

and that displays the response in the method render() by using the "response" variable.

However, this is not working -> the initial value "" is displayed. The HTTP-Request is working (tested), the HTTP-Response is recieved and correct(also tested), so perhaps the program is just not waiting untill the http request is done and instead takes the initial value for "response".

How can i fix this, i.e. how can i enforce that response is set to the HTTP-response?