use System\Classes\CombineAssets;

public function onEnd()
{
$assets = [
"assets/js/jquery.min.js",
"assets/js/jquery.easing.1.3.js",
"assets/layerslider/js/greensock.js",
"assets/layerslider/js/layerslider.transitions.js",
"assets/js/jquery.ui.totop.js",
"assets/js/custom.js",
];
$this->addJs(CombineAssets::combine($assets, $this->assetPath));
}

Error comes

We're sorry, but an unhandled error occurred. Please see the details below. The source "assets/js/jquery.min.js" is not in the root directory "/home/user/public_html"

/home/user/public_html/vendor/kriswallsmith/assetic/src/Assetic/Asset/FileAsset.php line 46 Followed this method: https://octobercms.com/forum/post/combining-a-set-of-javascript-files-within-a-component

Issue has been resolved

Hey kiitkp, can you post how you resolved the issue? It'd be helpful for anyone else down the road who might have the same issue.

Thanks!

Hi changed $this->assetPath to base_path('themes/themename')

This themes_path('theme-name') returns the same as base_path('themes/theme-name').