The site http://yacd.haishan.me is served with HTTP not HTTPS is because many browsers blocking request to HTTP resources from a HTTPS website. If you think it's not safe or not comfort with this, you can actually download the zip of the gh-pages, unzip and open index.html directly.
Extra note for Firefox users:
yacd is using the Fetch (Web) API to stream chunked API response from Clash to draw the traffic chart. But currently the streaming feature in Firefox needs to be turned on manually. Here is how to:
Visit about:config, search for dom.streams.enabled and javascript.options.streams, double click those items to turn them on.
# install dependencies
yarn
# start the dev server
yarn start
# go to http://127.0.0.1:3000