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env.md

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Env

The opaque data structure containing the environment in which the request is being run.

The Env object is usually created and passed by the Node.js runtime or node-addon-api infrastructure.

Methods

Constructor

Napi::Env::Env(napi_env env);
  • [in] env: The napi_env environment from which to construct the Napi::Env object.

napi_env

operator napi_env() const;

Returns the napi_env opaque data structure representing the environment.

Global

Napi::Object Napi::Env::Global() const;

Returns the Napi::Object representing the environment's JavaScript Global Object.

Undefined

Napi::Value Napi::Env::Undefined() const;

Returns the Napi::Value representing the environment's JavaScript Undefined Object.

Null

Napi::Value Napi::Env::Null() const;

Returns the Napi::Value representing the environment's JavaScript Null Object.

IsExceptionPending

bool Napi::Env::IsExceptionPending() const;

Returns a bool indicating if an exception is pending in the environment.

GetAndClearPendingException

Napi::Error Napi::Env::GetAndClearPendingException();

Returns an Napi::Error object representing the environment's pending exception, if any.

RunScript

Napi::Value Napi::Env::RunScript(____ script);
  • [in] script: A string containing JavaScript code to execute.

Runs JavaScript code contained in a string and returns its result.

The script can be any of the following types:

GetInstanceData

template <typename T> T* GetInstanceData();

Returns the instance data that was previously associated with the environment, or nullptr if none was associated.

SetInstanceData

template <typename T> using Finalizer = void (*)(Env, T*);
template <typename T, Finalizer<T> fini = Env::DefaultFini<T>>
void SetInstanceData(T* data);
  • [template] fini: A function to call when the instance data is to be deleted. Accepts a function of the form void CleanupData(Napi::Env env, T* data). If not given, the default finalizer will be used, which simply uses the delete operator to destroy T* when the addon instance is unloaded.
  • [in] data: A pointer to data that will be associated with the instance of the addon for the duration of its lifecycle.

Associates a data item stored at T* data with the current instance of the addon. The item will be passed to the function fini which gets called when an instance of the addon is unloaded.

SetInstanceData

template <typename DataType, typename HintType>
using FinalizerWithHint = void (*)(Env, DataType*, HintType*);
template <typename DataType,
          typename HintType,
          FinalizerWithHint<DataType, HintType> fini =
            Env::DefaultFiniWithHint<DataType, HintType>>
void SetInstanceData(DataType* data, HintType* hint);
  • [template] fini: A function to call when the instance data is to be deleted. Accepts a function of the form void CleanupData(Napi::Env env, DataType* data, HintType* hint). If not given, the default finalizer will be used, which simply uses the delete operator to destroy T* when the addon instance is unloaded.
  • [in] data: A pointer to data that will be associated with the instance of the addon for the duration of its lifecycle.
  • [in] hint: A pointer to data that will be associated with the instance of the addon for the duration of its lifecycle and will be passed as a hint to fini when the addon instance is unloaded.

Associates a data item stored at T* data with the current instance of the addon. The item will be passed to the function fini which gets called when an instance of the addon is unloaded. This overload accepts an additional hint to be passed to fini.

AddCleanupHook

template <typename Hook>
CleanupHook<Hook> AddCleanupHook(Hook hook);
  • [in] hook: A function to call when the environment exists. Accepts a function of the form void ().

Registers hook as a function to be run once the current Node.js environment exits. Unlike the underlying C-based Node-API, providing the same hook multiple times is allowed. The hooks will be called in reverse order, i.e. the most recently added one will be called first.

Returns an Env::CleanupHook object, which can be used to remove the hook via its Remove() method.

AddCleanupHook

template <typename Hook, typename Arg>
CleanupHook<Hook, Arg> AddCleanupHook(Hook hook, Arg* arg);
  • [in] hook: A function to call when the environment exists. Accepts a function of the form void (Arg* arg).
  • [in] arg: A pointer to data that will be passed as the argument to hook.

Registers hook as a function to be run with the arg parameter once the current Node.js environment exits. Unlike the underlying C-based Node-API, providing the same hook and arg pair multiple times is allowed. The hooks will be called in reverse order, i.e. the most recently added one will be called first.

Returns an Env::CleanupHook object, which can be used to remove the hook via its Remove() method.

Env::CleanupHook

The Env::CleanupHook object allows removal of the hook added via Env::AddCleanupHook()

Methods

IsEmpty

bool IsEmpty();

Returns true if the cleanup hook was not successfully registered.

Remove

bool Remove(Env env);

Unregisters the hook from running once the current Node.js environment exits.

Returns true if the hook was successfully removed from the Node.js environment.