Question
How do I add Javascript file to modern page
Answer
- Add Data View Plus web part to the page

- In template editor go to Scripts tab
- In script editor create new script loadJS:

- In the script editor add the code:

var script = document.createElement('script');
script.onload = function () {
//do stuff with the script
};
script.src = 'https://kwizcom.sharepoint.com/sites/st/SiteAssets/Test1.js';
document.head.appendChild(script); - Go back to HTML tab and add the code there: