程序代写代做代考 Java javascript ## New

## New

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.

– Nan::New()
– Nan::Undefined()
– Nan::Null()
– Nan::True()
– Nan::False()
– Nan::EmptyString()

### Nan::New()

`Nan::New()` should be used to instantiate new JavaScript objects.

Refer to the specific V8 type in the [V8 documentation](https://v8docs.nodesource.com/io.js-3.0/d1/d83/classv8_1_1_data.html) for information on the types of arguments required for instantiation.

Signatures:

Return types are mostly omitted from the signatures for simplicity. In most cases the type will be contained within a `v8::Local`. The following types will be contained within a `Nan::MaybeLocal`: `v8::String`, `v8::Date`, `v8::RegExp`, `v8::Script`, `v8::UnboundScript`.

Empty objects:

“`c++
Nan::New();
“`

Generic single and multiple-argument:

“`c++
Nan::New(A0 arg0);
Nan::New(A0 arg0, A1 arg1);
Nan::New(A0 arg0, A1 arg1, A2 arg2);
Nan::New(A0 arg0, A1 arg1, A2 arg2, A3 arg3);
“`

For creating `v8::FunctionTemplate` and `v8::Function` objects:

_The definition of `Nan::FunctionCallback` can be found in the [Method declaration](./methods.md#api_nan_method) documentation._

“`c++
Nan::New(Nan::FunctionCallback callback,
v8::Local data = v8::Local());
Nan::New(Nan::FunctionCallback callback,
v8::Local data = v8::Local(),
A2 a2 = A2());
“`

Native number types:

“`c++
v8::Local Nan::New(bool value);
v8::Local Nan::New(int32_t value);
v8::Local Nan::New(uint32_t value);
v8::Local Nan::New(double value);
“`

String types:

“`c++
Nan::MaybeLocal Nan::New(std::string const& value);
Nan::MaybeLocal Nan::New(const char * value, int length);
Nan::MaybeLocal Nan::New(const char * value);
Nan::MaybeLocal Nan::New(const uint16_t * value);
Nan::MaybeLocal Nan::New(const uint16_t * value, int length);
“`

Specialized types:

“`c++
v8::Local Nan::New(v8::String::ExternalStringResource * value);
v8::Local Nan::New(Nan::ExternalOneByteStringResource * value);
v8::Local Nan::New(v8::Local pattern, v8::RegExp::Flags flags);
“`

Note that `Nan::ExternalOneByteStringResource` maps to [`v8::String::ExternalOneByteStringResource`](https://v8docs.nodesource.com/io.js-3.0/d9/db3/classv8_1_1_string_1_1_external_one_byte_string_resource.html), and `v8::String::ExternalAsciiStringResource` in older versions of V8.

### Nan::Undefined()

A helper method to reference the `v8::Undefined` object in a way that is compatible across all supported versions of V8.

Signature:

“`c++
v8::Local Nan::Undefined()
“`

### Nan::Null()

A helper method to reference the `v8::Null` object in a way that is compatible across all supported versions of V8.

Signature:

“`c++
v8::Local Nan::Null()
“`

### Nan::True()

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.

Signature:

“`c++
v8::Local Nan::True()
“`

### Nan::False()

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.

Signature:

“`c++
v8::Local Nan::False()
“`

### Nan::EmptyString()

Call [`v8::String::Empty`](https://v8docs.nodesource.com/io.js-3.0/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.

Signature:

“`c++
v8::Local Nan::EmptyString()
“`

### Nan::NewOneByteString()

An implementation of [`v8::String::NewFromOneByte()`](https://v8docs.nodesource.com/io.js-3.0/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.

Signature:

“`c++
Nan::MaybeLocal Nan::NewOneByteString(const uint8_t * value,
int length = -1)
“`