The only way to detect proxies without mutating the object

proxy-detection.js

// Courtesy of: https://www.reddit.com/r/javascript/comments/4wrdxd/comment/d69j04s/

const proxies = new WeakSet();

function createProxy(target, handler) {
    const proxy = new Proxy(target, handler);
    proxies.add(proxy);
    return proxy;
}
function isProxy(obj) {
    return proxies.has(obj);
}