Custom Portal provides a means for adding custom JavaScript code to any Page. Add your JavaScript code as a Snippet in the JavaScript section of the Admin panel, rename it, and click Save.

Snippets that you create this way can be added to one or more Pages in the Page editor and will be run once the page loads. Multiple Snippets can be added and loaded in the desired order by dragging and dropping.

You can use JavaScript Snippets to perform tasks such as pulling data from a 3rd party API and displaying it in an HTML block. You can utilize the System JavaScript API to access data about the Page, Blocks, and more from your Snippet.