Mixed Content The page at was loaded over HTTPS but requested an insecure resource This request has been blocked the content must be served over HTTPS

There's no way to disable mixed content using javascript but you can add this tag

<meta http-equiv="Content-Security-Policy" content="upgrade-insecure-requests">

to your HTML to allow mixed content

to allow Mixed Content:
1- add this meta tag to the page (HTML File)

<meta http-equiv="Content-Security-Policy" content="upgrade-insecure-requests">

2- add unsafe_url for referrerPolicy to your fetch requests if you get ERR_CONNECTION_REFUSED
example:

fetch('http://URL', {
    // ...
    referrerPolicy: "unsafe_url" 
});

Warning: This policy will leak potentially-private information from HTTPS resource URLs to insecure origins. Carefully consider the impact of this setting.

for more info check these 2 documentations:

1. https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Referrer-Policy
2. https://javascript.info/fetch-api