Load external scripts asynchronously

I’d like to load external scripts asynchronously. For example: <script src=“demo_async.js” async></script>. But I’d like to use the function registerCoreScript(). Is there a way to do that? I tried to search the framework core files but I couldn’t find the place where I need to change.

Finally I found the place in the framework where I can modify the "async" value. It is in the function scriptFile, located in the class CHtml (framework > web > helpers > CHtml.php).