Discover key in js object

discover.js

let cache = new Set();

let discoverIn = function(obj, keyToFind, previousPath = "") {
    if(obj === null || typeof obj !== "object") {
        return;
    }
    
    if (cache.has(obj)) return;
    cache.add(obj);

    const keys = Object.keys(obj);
    for (let k of keys) {
        // ignore __ leading keys
        if (k.startsWith('__')) continue;

        if (k === keyToFind) {
            console.log("path : ", previousPath  + "." + k);
            break;
        }
        discoverIn(obj[k], keyToFind, previousPath + "." + k);
    }
}

discoverIn(form, "keytofind");