napi_define_class

napi_status napi_define_class(napi_env env,
                              const char* utf8name,
                              size_t length,
                              napi_callback constructor,
                              void* data,
                              size_t property_count,
                              const napi_property_descriptor* properties,
                              napi_value* result); 拷贝

• [in] env：调用 API 的环境。

  ¥[in] env: The environment that the API is invoked under.

• [in] utf8name：JavaScript 构造函数的名称。为清楚起见，建议在封装 C++ 类时使用 C++ 类名。

  ¥[in] utf8name: Name of the JavaScript constructor function. For clarity, it is recommended to use the C++ class name when wrapping a C++ class.

• [in] length：utf8name 的长度（以字节为单位）或 NAPI_AUTO_LENGTH（如果以 null 结尾）。

  ¥[in] length: The length of the utf8name in bytes, or NAPI_AUTO_LENGTH if it is null-terminated.

• [in] constructor：处理类的构造实例的回调函数。封装 C++ 类时，此方法必须是具有 napi_callback 签名的静态成员。不能使用 C++ 类构造函数。napi_callback 提供了更多详细信息。

  ¥[in] constructor: Callback function that handles constructing instances of the class. When wrapping a C++ class, this method must be a static member with the napi_callback signature. A C++ class constructor cannot be used. napi_callback provides more details.

• [in] data：作为回调信息的 data 属性传递给构造函数回调的可选数据。

  ¥[in] data: Optional data to be passed to the constructor callback as the data property of the callback info.

• [in] property_count：properties 数组参数中的项数。

  ¥[in] property_count: Number of items in the properties array argument.

• [in] properties：描述类静态和实例数据属性、访问器和方法的属性描述符数组 请参见 napi_property_descriptor。

  ¥[in] properties: Array of property descriptors describing static and instance data properties, accessors, and methods on the class See napi_property_descriptor.

• [out] result：表示类的构造函数的 napi_value。

  ¥[out] result: A napi_value representing the constructor function for the class.

如果 API 成功，则返回 napi_ok。

¥Returns napi_ok if the API succeeded.

定义一个 JavaScript 类，包括：

¥Defines a JavaScript class, including:

• 具有类名的 JavaScript 构造函数。当封装相应的 C++ 类时，通过 constructor 传递的回调可用于实例化一个新的 C++ 类实例，然后将其放置在使用 napi_wrap 构造的 JavaScript 对象实例中。

  ¥A JavaScript constructor function that has the class name. When wrapping a corresponding C++ class, the callback passed via constructor can be used to instantiate a new C++ class instance, which can then be placed inside the JavaScript object instance being constructed using napi_wrap.

• 构造函数上的属性，其实现可以调用 C++ 类的相应静态数据属性、访问器和方法（由具有 napi_static 属性的属性描述符定义）。

  ¥Properties on the constructor function whose implementation can call corresponding static data properties, accessors, and methods of the C++ class (defined by property descriptors with the napi_static attribute).

• 构造函数的 prototype 对象的属性。封装 C++ 类时，在检索放置在 JavaScript 对象实例中的 C++ 类实例后，可以从属性描述符中给定的静态函数调用 C++ 类的非静态数据属性、访问器和方法，而无需使用 napi_static 属性 napi_unwrap。

  ¥Properties on the constructor function's prototype object. When wrapping a C++ class, non-static data properties, accessors, and methods of the C++ class can be called from the static functions given in the property descriptors without the napi_static attribute after retrieving the C++ class instance placed inside the JavaScript object instance by using napi_unwrap.

封装 C++ 类时，通过 constructor 传递的 C++ 构造函数回调应该是调用实际类构造函数的类的静态方法，然后将新的 C++ 实例封装在 JavaScript 对象中，并返回封装器对象。详见 napi_wrap。

¥When wrapping a C++ class, the C++ constructor callback passed via constructor should be a static method on the class that calls the actual class constructor, then wraps the new C++ instance in a JavaScript object, and returns the wrapper object. See napi_wrap for details.

从 napi_define_class 返回的 JavaScript 构造函数通常被保存并在以后用于从原生代码构造类的新实例，和/或检查提供的值是否是类的实例。在这种情况下，为了防止函数值被垃圾收集，可以使用 napi_create_reference 创建对其的强持久引用，确保引用计数保持 >= 1。

¥The JavaScript constructor function returned from napi_define_class is often saved and used later to construct new instances of the class from native code, and/or to check whether provided values are instances of the class. In that case, to prevent the function value from being garbage-collected, a strong persistent reference to it can be created using napi_create_reference, ensuring that the reference count is kept >= 1.

通过 data 参数或 napi_property_descriptor 数组项的 data 字段传递给此 API 的任何非 NULL 数据都可以与生成的 JavaScript 构造函数（在 result 参数中返回）相关联，并在类为垃圾时释放 - 通过将 JavaScript 函数和数据传递给 napi_add_finalizer 来收集。

¥Any non-NULL data which is passed to this API via the data parameter or via the data field of the napi_property_descriptor array items can be associated with the resulting JavaScript constructor (which is returned in the result parameter) and freed whenever the class is garbage-collected by passing both the JavaScript function and the data to napi_add_finalizer.