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node_modules/node-addon-api/doc/addon.md

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+# Add-on Structure
+
+Class `Napi::Addon<T>` inherits from class [`Napi::InstanceWrap<T>`][].
+
+Creating add-ons that work correctly when loaded multiple times from the same
+source package into multiple Node.js threads and/or multiple times into the same
+Node.js thread requires that all global data they hold be associated with the
+environment in which they run. It is not safe to store global data in static
+variables because doing so does not take into account the fact that an add-on
+may be loaded into multiple threads nor that an add-on may be loaded multiple
+times into a single thread.
+
+The `Napi::Addon<T>` class can be used to define an entire add-on. Instances of
+`Napi::Addon<T>` subclasses become instances of the add-on, stored safely by
+Node.js on its various threads and into its various contexts. Thus, any data
+stored in the instance variables of a `Napi::Addon<T>` subclass instance are
+stored safely by Node.js. Functions exposed to JavaScript using
+`Napi::Addon<T>::InstanceMethod` and/or `Napi::Addon<T>::DefineAddon` are
+instance methods of the `Napi::Addon` subclass and thus have access to data
+stored inside the instance.
+
+`Napi::Addon<T>::DefineProperties` may be used to attach `Napi::Addon<T>`
+subclass instance methods to objects other than the one that will be returned to
+Node.js as the add-on instance.
+
+The `Napi::Addon<T>` class can be used together with the `NODE_API_ADDON()` and
+`NODE_API_NAMED_ADDON()` macros to define add-ons.
+
+## Example
+
+```cpp
+#include <napi.h>
+
+class ExampleAddon : public Napi::Addon<ExampleAddon> {
+ public:
+  ExampleAddon(Napi::Env env, Napi::Object exports) {
+    // In the constructor we declare the functions the add-on makes available
+    // to JavaScript.
+    DefineAddon(exports, {
+      InstanceMethod("increment", &ExampleAddon::Increment),
+
+      // We can also attach plain objects to `exports`, and instance methods as
+      // properties of those sub-objects.
+      InstanceValue("subObject", DefineProperties(Napi::Object::New(env), {
+        InstanceMethod("decrement", &ExampleAddon::Decrement)
+      }), napi_enumerable)
+    });
+  }
+ private:
+
+  // This method has access to the data stored in the environment because it is
+  // an instance method of `ExampleAddon` and because it was listed among the
+  // property descriptors passed to `DefineAddon()` in the constructor.
+  Napi::Value Increment(const Napi::CallbackInfo& info) {
+    return Napi::Number::New(info.Env(), ++value);
+  }
+
+  // This method has access to the data stored in the environment because it is
+  // an instance method of `ExampleAddon` and because it was exposed to
+  // JavaScript by calling `DefineProperties()` with the object onto which it is
+  // attached.
+  Napi::Value Decrement(const Napi::CallbackInfo& info) {
+    return Napi::Number::New(info.Env(), --value);
+  }
+
+  // Data stored in these variables is unique to each instance of the add-on.
+  uint32_t value = 42;
+};
+
+// The macro announces that instances of the class `ExampleAddon` will be
+// created for each instance of the add-on that must be loaded into Node.js.
+NODE_API_ADDON(ExampleAddon)
+```
+
+The above code can be used from JavaScript as follows:
+
+```js
+'use strict'
+
+const exampleAddon = require('bindings')('example_addon');
+console.log(exampleAddon.increment()); // prints 43
+console.log(exampleAddon.increment()); // prints 44
+console.log(exampleAddon.subObject.decrement()); // prints 43
+```
+
+When Node.js loads an instance of the add-on, a new instance of the class is
+created. Its constructor receives the environment `Napi::Env env` and the
+exports object `Napi::Object exports`. It can then use the method `DefineAddon`
+to either attach methods, accessors, and/or values to the `exports` object or to
+create its own `exports` object and attach methods, accessors, and/or values to
+it.
+
+Functions created with `Napi::Function::New()`, accessors created with
+`PropertyDescriptor::Accessor()`, and values can also be attached. If their
+implementation requires the `ExampleAddon` instance, it can be retrieved from
+the `Napi::Env env` with `GetInstanceData()`:
+
+```cpp
+void ExampleBinding(const Napi::CallbackInfo& info) {
+  ExampleAddon* addon = info.Env().GetInstanceData<ExampleAddon>();
+}
+```
+
+## Methods
+
+### Constructor
+
+Creates a new instance of the add-on.
+
+```cpp
+Napi::Addon(Napi::Env env, Napi::Object exports);
+```
+
+- `[in] env`: The environment into which the add-on is being loaded.
+- `[in] exports`: The exports object received from JavaScript.
+
+Typically, the constructor calls `DefineAddon()` to attach methods, accessors,
+and/or values to `exports`. The constructor may also create a new object and
+pass it to `DefineAddon()` as its first parameter if it wishes to replace the
+`exports` object as provided by Node.js.
+
+### DefineAddon
+
+Defines an add-on instance with functions, accessors, and/or values.
+
+```cpp
+template <typename T>
+void Napi::Addon<T>::DefineAddon(Napi::Object exports,
+                   const std::initializer_list<PropertyDescriptor>& properties);
+```
+
+* `[in] exports`: The object to return to Node.js as an instance of the add-on.
+* `[in] properties`: Initializer list of add-on property descriptors of the
+methods, property accessors, and values that define the add-on. They will be
+set on `exports`.
+See: [`Class property and descriptor`](class_property_descriptor.md).
+
+### DefineProperties
+
+Defines function, accessor, and/or value properties on an object using add-on
+instance methods.
+
+```cpp
+template <typename T>
+Napi::Object
+Napi::Addon<T>::DefineProperties(Napi::Object object,
+                   const std::initializer_list<PropertyDescriptor>& properties);
+```
+
+* `[in] object`: The object that will receive the new properties.
+* `[in] properties`: Initializer list of property descriptors of the methods,
+property accessors, and values to attach to `object`.
+See: [`Class property and descriptor`](class_property_descriptor.md).
+
+Returns `object`.
+
+[`Napi::InstanceWrap<T>`]: ./instance_wrap.md