[SOLVED] js c++ Java javascript data structure ## JavaScript-accessible methods

## JavaScript-accessible methods

A _template_ is a blueprint for JavaScript functions and objects in a context. You can use a template to wrap C++ functions and data structures within JavaScript objects so that they can be manipulated from JavaScript. See the V8 Embedders Guide section on [Templates](https://developers.google.com/v8/embed#templates) for further information.

In order to expose functionality to JavaScript via a template, you must provide it to V8 in a form that it understands. Across the versions of V8 supported by NAN, JavaScript-accessible method signatures vary widely, NAN fully abstracts method declaration and provides you with an interface that is similar to the most recent V8 API but is backward-compatible with older versions that still use the now-deceased `v8::Argument` type.

* **Method argument types**
Nan::FunctionCallbackInfo
Nan::PropertyCallbackInfo
Nan::ReturnValue
* **Method declarations**
Method declaration
Getter declaration
Setter declaration
Property getter declaration
Property setter declaration
Property enumerator declaration
Property deleter declaration
Property query declaration
Index getter declaration
Index setter declaration
Index enumerator declaration
Index deleter declaration
Index query declaration
* Method and template helpers
Nan::SetMethod()
Nan::SetPrototypeMethod()
Nan::SetAccessor()
Nan::SetNamedPropertyHandler()
Nan::SetIndexedPropertyHandler()
Nan::SetTemplate()
Nan::SetPrototypeTemplate()
Nan::SetInstanceTemplate()
Nan::SetCallHandler()
Nan::SetCallAsFunctionHandler()

### Nan::FunctionCallbackInfo

`Nan::FunctionCallbackInfo` should be used in place of [`v8::FunctionCallbackInfo`](https://v8docs.nodesource.com/io.js-3.0/dd/d0d/classv8_1_1_function_callback_info.html), even with older versions of Node where `v8::FunctionCallbackInfo` does not exist.

Definition:

`c++
template class FunctionCallbackInfo {
public:
ReturnValue GetReturnValue() const;
v8::Local Callee();
v8::Local Data();
v8::Local Holder();
bool IsConstructCall();
int Length() const;
v8::Local operator[](int i) const;
v8::Local This() const;
v8::Isolate *GetIsolate() const;
};
`

See the [`v8::FunctionCallbackInfo`](https://v8docs.nodesource.com/io.js-3.0/dd/d0d/classv8_1_1_function_callback_info.html) documentation for usage details on these. See [`Nan::ReturnValue`](#api_nan_return_value) for further information on how to set a return value from methods.

### Nan::PropertyCallbackInfo

`Nan::PropertyCallbackInfo` should be used in place of [`v8::PropertyCallbackInfo`](https://v8docs.nodesource.com/io.js-3.0/d7/dc5/classv8_1_1_property_callback_info.html), even with older versions of Node where `v8::PropertyCallbackInfo` does not exist.

Definition:

`c++
template class PropertyCallbackInfo : public PropertyCallbackInfoBase {
public:
ReturnValue GetReturnValue() const;
v8::Isolate* GetIsolate() const;
v8::Local Data() const;
v8::Local This() const;
v8::Local Holder() const;
};
`

See the [`v8::PropertyCallbackInfo`](https://v8docs.nodesource.com/io.js-3.0/d7/dc5/classv8_1_1_property_callback_info.html) documentation for usage details on these. See [`Nan::ReturnValue`](#api_nan_return_value) for further information on how to set a return value from property accessor methods.

### Nan::ReturnValue

`Nan::ReturnValue` is used in place of [`v8::ReturnValue`](https://v8docs.nodesource.com/io.js-3.0/da/da7/classv8_1_1_return_value.html) on both [`Nan::FunctionCallbackInfo`](#api_nan_function_callback_info) and [`Nan::PropertyCallbackInfo`](#api_nan_property_callback_info) as the return type of `GetReturnValue()`.

Example usage:

`c++
void EmptyArray(const Nan::FunctionCallbackInfo & info) {
info.GetReturnValue().Set(Nan::New ());
}
`

Definition:

`c++
template class ReturnValue {
public:
// Handle setters
template void Set(const v8::Local &handle);
template void Set(const Nan::Global &handle);

// Fast primitive setters
void Set(bool value);
void Set(double i);
void Set(int32_t i);
void Set(uint32_t i);

// Fast JS primitive setters
void SetNull();
void SetUndefined();
void SetEmptyString();

// Convenience getter for isolate
v8::Isolate *GetIsolate() const;
};
`

See the documentation on [`v8::ReturnValue`](https://v8docs.nodesource.com/io.js-3.0/da/da7/classv8_1_1_return_value.html) for further information on this.

### Method declaration

JavaScript-accessible methods should be declared with the following signature to form a `Nan::FunctionCallback`:

`c++
typedef void(*FunctionCallback)(const FunctionCallbackInfo &);
`

Example:

`c++
void MethodName(const Nan::FunctionCallbackInfo & info) {

}
`

You do not need to declare a new `HandleScope` within a method as one is implicitly created for you.

**Example usage**

`c++
// .h:
class Foo : public Nan::ObjectWrap {

static void Bar(const Nan::FunctionCallbackInfo & info);
static void Baz(const Nan::FunctionCallbackInfo & info);
}

// .cc:
void Foo::Bar(const Nan::FunctionCallbackInfo & info) {

}

void Foo::Baz(const Nan::FunctionCallbackInfo & info) {

}
`

A helper macro `NAN_METHOD(methodname)` exists, compatible with NAN v1 method declarations.

**Example usage with `NAN_METHOD(methodname)`**

`c++
// .h:
class Foo : public Nan::ObjectWrap {

static NAN_METHOD(Bar);
static NAN_METHOD(Baz);
}

// .cc:
NAN_METHOD(Foo::Bar) {

}

NAN_METHOD(Foo::Baz) {

}
`

Use [`Nan::SetPrototypeMethod`](#api_nan_set_prototype_method) to attach a method to a JavaScript function prototype or [`Nan::SetMethod`](#api_nan_set_method) to attach a method directly on a JavaScript object.

### Getter declaration

JavaScript-accessible getters should be declared with the following signature to form a `Nan::GetterCallback`:

`c++
typedef void(*GetterCallback)(v8::Local ,
const PropertyCallbackInfo &);
`

Example:

`c++
void GetterName(v8::Local property,
const Nan::PropertyCallbackInfo & info) {

}
`

You do not need to declare a new `HandleScope` within a getter as one is implicitly created for you.

A helper macro `NAN_GETTER(methodname)` exists, compatible with NAN v1 method declarations.

Also see the V8 Embedders Guide documentation on [Accessors](https://developers.google.com/v8/embed#accesssors).

### Setter declaration

JavaScript-accessible setters should be declared with the following signature to form a Nan::SetterCallback :

`c++
typedef void(*SetterCallback)(v8::Local ,
v8::Local ,
const PropertyCallbackInfo &);
`

Example:

`c++
void SetterName(v8::Local property,
v8::Local value,
const Nan::PropertyCallbackInfo & info) {

}
`

You do not need to declare a new `HandleScope` within a setter as one is implicitly created for you.

A helper macro `NAN_SETTER(methodname)` exists, compatible with NAN v1 method declarations.

Also see the V8 Embedders Guide documentation on [Accessors](https://developers.google.com/v8/embed#accesssors).

### Property getter declaration

JavaScript-accessible property getters should be declared with the following signature to form a Nan::PropertyGetterCallback :

`c++
typedef void(*PropertyGetterCallback)(v8::Local ,
const PropertyCallbackInfo &);
`

Example:

`c++
void PropertyGetterName(v8::Local property,
const Nan::PropertyCallbackInfo & info) {

}
`

You do not need to declare a new `HandleScope` within a property getter as one is implicitly created for you.

A helper macro `NAN_PROPERTY_GETTER(methodname)` exists, compatible with NAN v1 method declarations.

Also see the V8 Embedders Guide documentation on named property [Interceptors](https://developers.google.com/v8/embed#interceptors).

### Property setter declaration

JavaScript-accessible property setters should be declared with the following signature to form a Nan::PropertySetterCallback :

`c++
typedef void(*PropertySetterCallback)(v8::Local ,
v8::Local ,
const PropertyCallbackInfo &);
`

Example:

`c++
void PropertySetterName(v8::Local property,
v8::Local value,
const Nan::PropertyCallbackInfo & info);
`

You do not need to declare a new `HandleScope` within a property setter as one is implicitly created for you.

A helper macro `NAN_PROPERTY_SETTER(methodname)` exists, compatible with NAN v1 method declarations.

Also see the V8 Embedders Guide documentation on named property [Interceptors](https://developers.google.com/v8/embed#interceptors).

### Property enumerator declaration

JavaScript-accessible property enumerators should be declared with the following signature to form a Nan::PropertyEnumeratorCallback :

`c++
typedef void(*PropertyEnumeratorCallback)(const PropertyCallbackInfo &);
`

Example:

`c++
void PropertyEnumeratorName(const Nan::PropertyCallbackInfo & info);
`

You do not need to declare a new `HandleScope` within a property enumerator as one is implicitly created for you.

A helper macro `NAN_PROPERTY_ENUMERATOR(methodname)` exists, compatible with NAN v1 method declarations.

Also see the V8 Embedders Guide documentation on named property [Interceptors](https://developers.google.com/v8/embed#interceptors).

### Property deleter declaration

JavaScript-accessible property deleters should be declared with the following signature to form a Nan::PropertyDeleterCallback :

`c++
typedef void(*PropertyDeleterCallback)(v8::Local ,
const PropertyCallbackInfo &);
`

Example:

`c++
void PropertyDeleterName(v8::Local property,
const Nan::PropertyCallbackInfo & info);
`

You do not need to declare a new `HandleScope` within a property deleter as one is implicitly created for you.

A helper macro `NAN_PROPERTY_DELETER(methodname)` exists, compatible with NAN v1 method declarations.

Also see the V8 Embedders Guide documentation on named property [Interceptors](https://developers.google.com/v8/embed#interceptors).

### Property query declaration

JavaScript-accessible property query methods should be declared with the following signature to form a Nan::PropertyQueryCallback :

`c++
typedef void(*PropertyQueryCallback)(v8::Local ,
const PropertyCallbackInfo &);
`

Example:

`c++
void PropertyQueryName(v8::Local property,
const Nan::PropertyCallbackInfo & info);
`

You do not need to declare a new `HandleScope` within a property query method as one is implicitly created for you.

A helper macro `NAN_PROPERTY_QUERY(methodname)` exists, compatible with NAN v1 method declarations.

Also see the V8 Embedders Guide documentation on named property [Interceptors](https://developers.google.com/v8/embed#interceptors).

### Index getter declaration

JavaScript-accessible index getter methods should be declared with the following signature to form a Nan::IndexGetterCallback :

`c++
typedef void(*IndexGetterCallback)(uint32_t,
const PropertyCallbackInfo &);
`

Example:

`c++
void IndexGetterName(uint32_t index, const PropertyCallbackInfo & info);
`

You do not need to declare a new `HandleScope` within a index getter as one is implicitly created for you.

A helper macro `NAN_INDEX_GETTER(methodname)` exists, compatible with NAN v1 method declarations.

Also see the V8 Embedders Guide documentation on indexed property [Interceptors](https://developers.google.com/v8/embed#interceptors).

### Index setter declaration

JavaScript-accessible index setter methods should be declared with the following signature to form a Nan::IndexSetterCallback :

`c++
typedef void(*IndexSetterCallback)(uint32_t,
v8::Local ,
const PropertyCallbackInfo &);
`

Example:

`c++
void IndexSetterName(uint32_t index,
v8::Local value,
const PropertyCallbackInfo & info);
`

You do not need to declare a new `HandleScope` within a index setter as one is implicitly created for you.

A helper macro `NAN_INDEX_SETTER(methodname)` exists, compatible with NAN v1 method declarations.

Also see the V8 Embedders Guide documentation on indexed property [Interceptors](https://developers.google.com/v8/embed#interceptors).

### Index enumerator declaration

JavaScript-accessible index enumerator methods should be declared with the following signature to form a Nan::IndexEnumeratorCallback :

`c++
typedef void(*IndexEnumeratorCallback)(const PropertyCallbackInfo &);
`

Example:

`c++
void IndexEnumeratorName(const PropertyCallbackInfo & info);
`

You do not need to declare a new `HandleScope` within a index enumerator as one is implicitly created for you.

A helper macro `NAN_INDEX_ENUMERATOR(methodname)` exists, compatible with NAN v1 method declarations.

Also see the V8 Embedders Guide documentation on indexed property [Interceptors](https://developers.google.com/v8/embed#interceptors).

### Index deleter declaration

JavaScript-accessible index deleter methods should be declared with the following signature to form a Nan::IndexDeleterCallback :

`c++
typedef void(*IndexDeleterCallback)(uint32_t,
const PropertyCallbackInfo &);
`

Example:

`c++
void IndexDeleterName(uint32_t index, const PropertyCallbackInfo & info);
`

You do not need to declare a new `HandleScope` within a index deleter as one is implicitly created for you.

A helper macro `NAN_INDEX_DELETER(methodname)` exists, compatible with NAN v1 method declarations.

Also see the V8 Embedders Guide documentation on indexed property [Interceptors](https://developers.google.com/v8/embed#interceptors).

### Index query declaration

JavaScript-accessible index query methods should be declared with the following signature to form a Nan::IndexQueryCallback :

`c++
typedef void(*IndexQueryCallback)(uint32_t,
const PropertyCallbackInfo &);
`

Example:

`c++
void IndexQueryName(uint32_t index, const PropertyCallbackInfo & info);
`

You do not need to declare a new `HandleScope` within a index query method as one is implicitly created for you.

A helper macro `NAN_INDEX_QUERY(methodname)` exists, compatible with NAN v1 method declarations.

Also see the V8 Embedders Guide documentation on indexed property [Interceptors](https://developers.google.com/v8/embed#interceptors).

### Nan::SetMethod()

Sets a method with a given name directly on a JavaScript object where the method has the `Nan::FunctionCallback` signature (see Method declaration).

Signature:

`c++
void Nan::SetMethod(v8::Local recv,
const char *name,
Nan::FunctionCallback callback)
void Nan::SetMethod(v8::Local templ,
const char *name,
Nan::FunctionCallback callback)
`

### Nan::SetPrototypeMethod()

Sets a method with a given name on a `FunctionTemplate`s prototype where the method has the `Nan::FunctionCallback` signature (see Method declaration).

Signature:

`c++
void Nan::SetPrototypeMethod(v8::Local recv,
const char* name,
Nan::FunctionCallback callback)
`

### Nan::SetAccessor()

Sets getters and setters for a property with a given name on an `ObjectTemplate` or a plain `Object`. Accepts getters with the `Nan::GetterCallback` signature (see Getter declaration) and setters with the `Nan::SetterCallback` signature (see Setter declaration).

Signature:

`c++
void SetAccessor(v8::Local tpl,
v8::Local name,
Nan::GetterCallback getter,
Nan::SetterCallback setter = 0,
v8::Local data = v8::Local (),
v8::AccessControl settings = v8::DEFAULT,
v8::PropertyAttribute attribute = v8::None,
imp::Sig signature = imp::Sig());
bool SetAccessor(v8::Local obj,
v8::Local name,
Nan::GetterCallback getter,
Nan::SetterCallback setter = 0,
v8::Local data = v8::Local (),
v8::AccessControl settings = v8::DEFAULT,
v8::PropertyAttribute attribute = v8::None)
`

See the V8 [`ObjectTemplate#SetAccessor()`](https://v8docs.nodesource.com/io.js-3.0/db/d5f/classv8_1_1_object_template.html#aa90691622f01269c6a11391d372ca0c5) and [`Object#SetAccessor()`](https://v8docs.nodesource.com/io.js-3.0/db/d85/classv8_1_1_object.html#a3f9dee085f5ec346465f1dc924325043) for further information about how to use `Nan::SetAccessor()`.

### Nan::SetNamedPropertyHandler()

Sets named property getters, setters, query, deleter and enumerator methods on an `ObjectTemplate`. Accepts:

* Property getters with the `Nan::PropertyGetterCallback` signature (see Property getter declaration)
* Property setters with the `Nan::PropertySetterCallback` signature (see Property setter declaration)
* Property query methods with the `Nan::PropertyQueryCallback` signature (see Property query declaration)
* Property deleters with the `Nan::PropertyDeleterCallback` signature (see Property deleter declaration)
* Property enumerators with the `Nan::PropertyEnumeratorCallback` signature (see Property enumerator declaration)

Signature:

`c++
void SetNamedPropertyHandler(v8::Local tpl,
Nan::PropertyGetterCallback getter,
Nan::PropertySetterCallback setter = 0,
Nan::PropertyQueryCallback query = 0,
Nan::PropertyDeleterCallback deleter = 0,
Nan::PropertyEnumeratorCallback enumerator = 0,
v8::Local data = v8::Local ())
`

See the V8 [`ObjectTemplate#SetNamedPropertyHandler()`](https://v8docs.nodesource.com/io.js-3.0/db/d5f/classv8_1_1_object_template.html#a34d1cc45b642cd131706663801aadd76) for further information about how to use `Nan::SetNamedPropertyHandler()`.

### Nan::SetIndexedPropertyHandler()

Sets indexed property getters, setters, query, deleter and enumerator methods on an `ObjectTemplate`. Accepts:

* Indexed property getters with the `Nan::IndexGetterCallback` signature (see Index getter declaration)
* Indexed property setters with the `Nan::IndexSetterCallback` signature (see Index setter declaration)
* Indexed property query methods with the `Nan::IndexQueryCallback` signature (see Index query declaration)
* Indexed property deleters with the `Nan::IndexDeleterCallback` signature (see Index deleter declaration)
* Indexed property enumerators with the `Nan::IndexEnumeratorCallback` signature (see Index enumerator declaration)

Signature:

`c++
void SetIndexedPropertyHandler(v8::Local tpl,
Nan::IndexGetterCallback getter,
Nan::IndexSetterCallback setter = 0,
Nan::IndexQueryCallback query = 0,
Nan::IndexDeleterCallback deleter = 0,
Nan::IndexEnumeratorCallback enumerator = 0,
v8::Local data = v8::Local ())
`

See the V8 [`ObjectTemplate#SetIndexedPropertyHandler()`](https://v8docs.nodesource.com/io.js-3.0/db/d5f/classv8_1_1_object_template.html#ac0234cbede45d51778bb5f6a32a9e125) for further information about how to use `Nan::SetIndexedPropertyHandler()`.

### Nan::SetTemplate()

Adds properties on an `Object`s or `Function`s template.

Signature:

`c++
void Nan::SetTemplate(v8::Local templ,
const char *name,
v8::Local value);
void Nan::SetTemplate(v8::Local templ,
v8::Local name,
v8::Local value,
v8::PropertyAttribute attributes)
`

Calls the `Template`s [`Set()`](https://v8docs.nodesource.com/io.js-3.0/db/df7/classv8_1_1_template.html#a2db6a56597bf23c59659c0659e564ddf).

### Nan::SetPrototypeTemplate()

Adds properties on an `Object`s or `Function`s prototype template.

Signature:

`c++
void Nan::SetPrototypeTemplate(v8::Local templ,
const char *name,
v8::Local value);
void Nan::SetPrototypeTemplate(v8::Local templ,
v8::Local name,
v8::Local value,
v8::PropertyAttribute attributes)
`

Calls the `FunctionTemplate`s _PrototypeTemplates_ [`Set()`](https://v8docs.nodesource.com/io.js-3.0/db/df7/classv8_1_1_template.html#a2db6a56597bf23c59659c0659e564ddf).

### Nan::SetInstanceTemplate()

Use to add instance properties on `FunctionTemplate`s.

Signature:

`c++
void Nan::SetInstanceTemplate(v8::Local templ,
const char *name,
v8::Local value);
void Nan::SetInstanceTemplate(v8::Local templ,
v8::Local name,
v8::Local value,
v8::PropertyAttribute attributes)
`

Calls the `FunctionTemplate`s _InstanceTemplates_ [`Set()`](https://v8docs.nodesource.com/io.js-3.0/db/df7/classv8_1_1_template.html#a2db6a56597bf23c59659c0659e564ddf).

### Nan::SetCallHandler()

Set the call-handler callback for a `v8::FunctionTemplate`.
This callback is called whenever the function created from this FunctionTemplate is called.

Signature:

`c++
void Nan::SetCallHandler(v8::Local templ, Nan::FunctionCallback callback, v8::Local data = v8::Local ())
`

Calls the `FunctionTemplate`s [`SetCallHandler()`](https://v8docs.nodesource.com/io.js-3.0/d8/d83/classv8_1_1_function_template.html#a26cf14e36aa1a47091b98536d08ea821).

### Nan::SetCallAsFunctionHandler()

Sets the callback to be used when calling instances created from the `v8::ObjectTemplate` as a function.
If no callback is set, instances behave like normal JavaScript objects that cannot be called as a function.

Signature:

`c++
void Nan::SetCallAsFunctionHandler(v8::Local templ, Nan::FunctionCallback callback, v8::Local data = v8::Local ())
`

Calls the `ObjectTemplate`s [`SetCallAsFunctionHandler()`](https://v8docs.nodesource.com/io.js-3.0/db/d5f/classv8_1_1_object_template.html#ae0a0e72fb0c5e5f32e255fe5bcc7316a).