Is there a way to identify Persistent<Function> uniqueness? - c++

Question

I am storing js callbacks in vector:
std::vector<std::unique_ptr<Persistent<Function>>> callbacks;
Everything is working fine. The problem is that I do not want to store duplicated callbacks because I do not want to notify the same callback twice. I have to compare them somehow. Here is my full function but that does not work:
void ProcessCallback(const FunctionCallbackInfo<Value>& args)
{
std::string returnInfo;
Isolate* isolate = args.GetIsolate();
Local<Function> notifyFunction = Local<Function>::Cast(args[0]);
auto predicate = [&](const std::unique_ptr<Persistent<Function>>& c)
{
return c->Get(isolate)->StrictEquals(notifyFunction);
};
auto it = std::find_if(callbacks.begin(), callbacks.end(), predicate);
if (it == callbacks.end())
{
returnInfo = "Did not find callback. Adding..." + std::to_string(callbacks.size());
auto persistentCallback = std::make_unique<Persistent<Function>>(isolate, notifyFunction);
callbacks.emplace_back(std::move(persistentCallback));
}
else
{
returnInfo = "Callback already exist in a list.\n";
}
args.GetReturnValue().Set(String::NewFromUtf8(isolate, returnInfo.c_str()).ToLocalChecked());
}
In js:
function callback(msg) {
console.log(msg);
}
let addon = require('./build/Release/addon');
console.log(addon.on(callback));
console.log(addon.on(callback));
Is there something that I can rely on to uniquely identify function that is passed from js? Thanks.