How to reset the value of V8-variable?

How to set value for variable V8 in undefined?
Suppose there is a global variable:
Persistent<function> callback;</function>
How to set it to undefinedto free up memory (although I suspect it'll do GC).
September 26th 19 at 07:29
2 answers
September 26th 19 at 07:31
delete callback;
September 26th 19 at 07:33
Stupid forehead
obj->Set(v8::String::New("propname"), v8::Undefined());
not roll?

Read the question:
Generally Persistent, there is a Dispose method
callback.Dispose()

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