@stdlib/assert/napi/is-type/README.md

Standard assertion utilities.

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# Assert Type

> Assert that a Node-API value is a specified Node-API data type.

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## Usage

```javascript
var headerDir = require( '@stdlib/assert/napi/is-type' );
```

#### headerDir

Absolute file path for the directory containing header files for C APIs.

```javascript
var dir = headerDir;
// returns <string>
```

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## Examples

```javascript
var headerDir = require( '@stdlib/assert/napi/is-type' );

console.log( headerDir );
// => <string>
```

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* * *

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## C APIs

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### Usage

```c
#include "stdlib/assert/napi/is_type.h"
```

#### stdlib_assert_napi_value_is_type( env, value, type, \*message, \*err )

Asserts that a Node-API value is a specified Node-API data type.

```c
#include "stdlib/assert/napi/is_type.h"
#include <node_api.h>

static napi_value addon( napi_env env, napi_callback_info info ) {
    napi_value value;

    // ...

    napi_value err;
    napi_status status = stdlib_assert_napi_value_is_type( env, value, napi_number, "Must be a number.", &err );
    assert( status == napi_ok );
    if ( err != NULL ) {
        assert( napi_throw( env, err ) == napi_ok );
        return NULL;
    }

    // ...
}
```

The function accepts the following arguments:

-   **env**: `[in] napi_env` environment under which the function is invoked.
-   **value**: `[in] napi_value` Node-API value.
-   **type**: `[in] napi_valuetype` Node-API data type.
-   **message**: `[in] char*` error message.
-   **err**: `[out] napi_value*` pointer for storing a JavaScript error.

```c
napi_status stdlib_assert_napi_value_is_type( const napi_env env, const napi_value value, const napi_valuetype type, const char *message, napi_value *err );
```

The function returns a `napi_status` status code indicating success or failure (returns `napi_ok` if success).

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### Notes

-   If provided a `value` whose type differs from `type`, the function sets `err` with a JavaScript error; otherwise, `err` is set to `NULL`.

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