Using graph theory to clone JavaScript objects with circular references

clone.js

function isObject(entity) {
    return typeof entity === "object" && entity !== null;
}

function cloneNonObjectProperties(obj) {
    return Object.fromEntries(
        Object.entries(obj).filter(([, v]) => !isObject(v))
    )
}

function getAdjacentNodes(obj) {
    return (
        Object.entries(obj)
        .filter(([, v]) => isObject(v))
    )
}

function cloneGraph(obj) {
    return cloneNode(obj, new Map())
}

function cloneNode(obj, helperDict) {

    // if we have already encountered this node
    // we can just return its clone reference
    if(helperDict.has(obj)) {
        return helperDict.get(obj)
    }

    // otherwise we start by cloning non object properties
    const clonedNode = cloneNonObjectProperties(obj);

    // then we set the just cloned reference as the obj clone
    // to avoid reworks on it
    helperDict.set(obj, clonedNode)

    // now we recursively clone each object reachable by the current node
    for (const [k, n] of getAdjacentNodes(obj)) {
        const clonedAdjacentNode = cloneNode(n, helperDict);

        // we can set the new reference on the cloned obj
        clonedNode[k] = clonedAdjacentNode
    }

    return clonedNode;
}