148 lines
4.7 KiB
Markdown
148 lines
4.7 KiB
Markdown
## New
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NAN provides a `Nan::New()` helper for the creation of new JavaScript objects in a way that's compatible across the supported versions of V8.
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- <a href="#api_nan_new"><b><code>Nan::New()</code></b></a>
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- <a href="#api_nan_undefined"><b><code>Nan::Undefined()</code></b></a>
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- <a href="#api_nan_null"><b><code>Nan::Null()</code></b></a>
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- <a href="#api_nan_true"><b><code>Nan::True()</code></b></a>
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- <a href="#api_nan_false"><b><code>Nan::False()</code></b></a>
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- <a href="#api_nan_empty_string"><b><code>Nan::EmptyString()</code></b></a>
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<a name="api_nan_new"></a>
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### Nan::New()
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`Nan::New()` should be used to instantiate new JavaScript objects.
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Refer to the specific V8 type in the [V8 documentation](https://v8docs.nodesource.com/node-8.16/d1/d83/classv8_1_1_data.html) for information on the types of arguments required for instantiation.
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Signatures:
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Return types are mostly omitted from the signatures for simplicity. In most cases the type will be contained within a `v8::Local<T>`. The following types will be contained within a `Nan::MaybeLocal<T>`: `v8::String`, `v8::Date`, `v8::RegExp`, `v8::Script`, `v8::UnboundScript`.
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Empty objects:
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```c++
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Nan::New<T>();
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```
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Generic single and multiple-argument:
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```c++
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Nan::New<T>(A0 arg0);
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Nan::New<T>(A0 arg0, A1 arg1);
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Nan::New<T>(A0 arg0, A1 arg1, A2 arg2);
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Nan::New<T>(A0 arg0, A1 arg1, A2 arg2, A3 arg3);
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```
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For creating `v8::FunctionTemplate` and `v8::Function` objects:
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_The definition of `Nan::FunctionCallback` can be found in the [Method declaration](./methods.md#api_nan_method) documentation._
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```c++
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Nan::New<T>(Nan::FunctionCallback callback,
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v8::Local<v8::Value> data = v8::Local<v8::Value>());
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Nan::New<T>(Nan::FunctionCallback callback,
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v8::Local<v8::Value> data = v8::Local<v8::Value>(),
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A2 a2 = A2());
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```
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Native number types:
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```c++
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v8::Local<v8::Boolean> Nan::New<T>(bool value);
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v8::Local<v8::Int32> Nan::New<T>(int32_t value);
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v8::Local<v8::Uint32> Nan::New<T>(uint32_t value);
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v8::Local<v8::Number> Nan::New<T>(double value);
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```
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String types:
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```c++
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Nan::MaybeLocal<v8::String> Nan::New<T>(std::string const& value);
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Nan::MaybeLocal<v8::String> Nan::New<T>(const char * value, int length);
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Nan::MaybeLocal<v8::String> Nan::New<T>(const char * value);
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Nan::MaybeLocal<v8::String> Nan::New<T>(const uint16_t * value);
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Nan::MaybeLocal<v8::String> Nan::New<T>(const uint16_t * value, int length);
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```
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Specialized types:
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```c++
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v8::Local<v8::String> Nan::New<T>(v8::String::ExternalStringResource * value);
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v8::Local<v8::String> Nan::New<T>(Nan::ExternalOneByteStringResource * value);
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v8::Local<v8::RegExp> Nan::New<T>(v8::Local<v8::String> pattern, v8::RegExp::Flags flags);
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```
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Note that `Nan::ExternalOneByteStringResource` maps to [`v8::String::ExternalOneByteStringResource`](https://v8docs.nodesource.com/node-8.16/d9/db3/classv8_1_1_string_1_1_external_one_byte_string_resource.html), and `v8::String::ExternalAsciiStringResource` in older versions of V8.
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<a name="api_nan_undefined"></a>
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### Nan::Undefined()
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A helper method to reference the `v8::Undefined` object in a way that is compatible across all supported versions of V8.
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Signature:
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```c++
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v8::Local<v8::Primitive> Nan::Undefined()
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```
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<a name="api_nan_null"></a>
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### Nan::Null()
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A helper method to reference the `v8::Null` object in a way that is compatible across all supported versions of V8.
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Signature:
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```c++
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v8::Local<v8::Primitive> Nan::Null()
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```
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<a name="api_nan_true"></a>
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### Nan::True()
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A helper method to reference the `v8::Boolean` object representing the `true` value in a way that is compatible across all supported versions of V8.
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Signature:
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```c++
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v8::Local<v8::Boolean> Nan::True()
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```
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<a name="api_nan_false"></a>
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### Nan::False()
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A helper method to reference the `v8::Boolean` object representing the `false` value in a way that is compatible across all supported versions of V8.
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Signature:
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```c++
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v8::Local<v8::Boolean> Nan::False()
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```
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<a name="api_nan_empty_string"></a>
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### Nan::EmptyString()
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Call [`v8::String::Empty`](https://v8docs.nodesource.com/node-8.16/d2/db3/classv8_1_1_string.html#a7c1bc8886115d7ee46f1d571dd6ebc6d) to reference the empty string in a way that is compatible across all supported versions of V8.
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Signature:
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```c++
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v8::Local<v8::String> Nan::EmptyString()
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```
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<a name="api_nan_new_one_byte_string"></a>
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### Nan::NewOneByteString()
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An implementation of [`v8::String::NewFromOneByte()`](https://v8docs.nodesource.com/node-8.16/d2/db3/classv8_1_1_string.html#a5264d50b96d2c896ce525a734dc10f09) provided for consistent availability and API across supported versions of V8. Allocates a new string from Latin-1 data.
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Signature:
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```c++
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Nan::MaybeLocal<v8::String> Nan::NewOneByteString(const uint8_t * value,
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int length = -1)
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```
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