object reference managed by the v8 garbage collector. • A local handle is a pointer to an object. All V8 objects are accessed using handles, they are necessary because of the way the V8 garbage collector works. • ⼀一个局部句句柄：⼀一个 v8 堆上的对象
for more than one function call, or when handle lifetimes do not correspond to C++ scopes. • A UniquePersistent<SomeType> handle relies on C++ constructors and destructors to manage the lifetime of the underlying object. • A Persistent<SomeType> can be constructed with its constructor, but must be explicitly cleared with Persistent::Reset.
that governs a number of local handles. • a container for any number of handles. When you've ﬁnished with your handles, instead of deleting each one individually you can simply delete their scope. • ⼀一个句句柄区域：N 个句句柄
a garbage collection cycle • “generational” processes only part of the object heap in most garbage collection cycles. This minimises the impact of stopping the application • “accurate” always knows exactly where all objects and pointers are in memory. This avoids falsely identifying objects as pointers which can result in memory leaks.
operations while active. • e.g.: a prepare handle gets its callback called once every loop iteration when active • e.g.: a TCP server handle get its connection callback called every time there is a new connection.
I/O is performed on non-blocking sockets which are polled using the best mechanism available on the given platform • the loop will block waiting for I/O activity on sockets which have been added to the poller and callbacks will be ﬁred indicating socket conditions (readable, writable hangup) so handles can read, write or perform the desired I/O operation.