title: Multiple ajax requests at the same time
body: <p>I have a bunch of images that I want to read with ajax.
  If I know the url of each image how can I make 3 image ajax requests simultaneously, then get the next 3 until I have them all?</p>
  
  <p>This is my ajax function for one image</p>
  
  <pre><code>  var image_url = images[i];
    var xhr = new XMLHttpRequest();
    xhr.onreadystatechange = function(){
      if(xhr.readyState == 4 &amp;&amp; xhr.status == 200){
        console.log(xhr.response, typeof xhr.response);
  
      }
    }
  
    xhr.open('GET', image_url);
    xhr.responseType = 'blob';
    xhr.send();
  </code></pre>