Recommendation: track when code has been fully downloaded and is ready for use…
Facts about scripts:
Each script tag blocks a page from continuing to render until it has fully downloaded.
Until a body tag is encountered, browsers do not start rendering anything on a page.
Scripts block downloading of all resources on a page.
It is recommended to put script tags at the bottom of your HTML page, just before you close your body tag, but, most important to remember (thus stated first and last): you obviously won’t use this if your script should be ready on “page load”.