# 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 ```cpp Napi::Env::Env(napi_env env); ``` - `[in] env`: The `napi_env` environment from which to construct the `Napi::Env` object. ### napi_env ```cpp operator napi_env() const; ``` Returns the `napi_env` opaque data structure representing the environment. ### Global ```cpp Napi::Object Napi::Env::Global() const; ``` Returns the `Napi::Object` representing the environment's JavaScript Global Object. ### Undefined ```cpp Napi::Value Napi::Env::Undefined() const; ``` Returns the `Napi::Value` representing the environment's JavaScript Undefined Object. ### Null ```cpp Napi::Value Napi::Env::Null() const; ``` Returns the `Napi::Value` representing the environment's JavaScript Null Object. ### IsExceptionPending ```cpp bool Napi::Env::IsExceptionPending() const; ``` Returns a `bool` indicating if an exception is pending in the environment. ### GetAndClearPendingException ```cpp Napi::Error Napi::Env::GetAndClearPendingException() const; ``` Returns an `Napi::Error` object representing the environment's pending exception, if any. ### RunScript ```cpp Napi::Value Napi::Env::RunScript(____ script) const; ``` - `[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: - [`Napi::String`](string.md) - `const char *` - `const std::string &` ### GetInstanceData ```cpp template T* GetInstanceData() const; ``` Returns the instance data that was previously associated with the environment, or `nullptr` if none was associated. ### SetInstanceData ```cpp template using Finalizer = void (*)(Env, T*); template fini = Env::DefaultFini> void SetInstanceData(T* data) const; ``` - `[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 ```cpp template using FinalizerWithHint = void (*)(Env, DataType*, HintType*); template fini = Env::DefaultFiniWithHint> void SetInstanceData(DataType* data, HintType* hint) const; ``` - `[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`. ### GetModuleFileName ```cpp const char* Napi::Env::GetModuleFileName() const; ``` Returns a A URL containing the absolute path of the location from which the add-on was loaded. For a file on the local file system it will start with `file://`. The string is null-terminated and owned by env and must thus not be modified or freed. It is only valid while the add-on is loaded. ### AddCleanupHook ```cpp template CleanupHook AddCleanupHook(Hook hook); ``` - `[in] hook`: A function to call when the environment exits. 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 ```cpp template CleanupHook AddCleanupHook(Hook hook, Arg* arg); ``` - `[in] hook`: A function to call when the environment exits. 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 ```cpp bool IsEmpty(); ``` Returns `true` if the cleanup hook was **not** successfully registered. ### Remove ```cpp 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.