What is the javascript alternative for ‘unordered_set’ / ‘unordered_map’ from c++, which give O(1) TC for ‘search’, ‘insert’ and ‘delete’?

Is there any similar implementation of ‘unordered_set’ / ‘unordered_map’ from c++, in javascript?

C++ Implementation

void someFunction(vector<int> &arr, int k){
    unordered_set<int> s(arr.begin(), arr.end());
    
    auto it = s.find(k); // TC: O(1)
    if(it != s.end())
        s.erase(k); // TC: O(1)
    else
        s.insert(k); // TC: O(1)
}

JS alternative try…

function someFunction(arr, k){
    let s = new set(arr);
    
    if(s.has(k)) // TC = ?
        s.delete(k); // TC = ?
    else
        s.add(k); // TC = ?
}