&gt;&gt;JavaScript, unlike a lot of other languages, never blocks<p>I think that&#x27;s a little strong.  It&#x27;s more like &quot;The group controlling Javascript has mostly tried to discourage introduction of things that block&quot;.<p>You can, for example, do a blocking XMLHttpRequest.  It&#x27;s deprecated, but possible.  <a href="https:&#x2F;&#x2F;jsfiddle.net&#x2F;923d5sda&#x2F;" rel="nofollow">https:&#x2F;&#x2F;jsfiddle.net&#x2F;923d5sda&#x2F;</a>