HTMLScriptElement: async property

The async property of the HTMLScriptElement interface is a boolean value that controls how the script should be executed. For classic scripts, if the async property is set to true, the external script will be fetched in parallel to parsing and evaluated as soon as it is available. For module scripts, if the async property is set to true, the script and all their dependencies will be fetched in parallel to parsing and evaluated as soon as they are available.

It reflects the async attribute of the <script> element.

<script id="el" src="/example.js" async></script>

const el = document.getElementById("el");
console.log(el.async); // Output: true