# <small>nlohmann::basic_json::</small>operator value_t

```cpp
constexpr operator value_t() const noexcept;
```

Return the type of the JSON value as a value from the [`value_t`](value_t.md) enumeration.
    
## Return value

the type of the JSON value

| Value type                | return value               |
|---------------------------|----------------------------|
| `#!json null`             | `value_t::null`            |
| boolean                   | `value_t::boolean`         |
| string                    | `value_t::string`          |
| number (integer)          | `value_t::number_integer`  |
| number (unsigned integer) | `value_t::number_unsigned` |
| number (floating-point)   | `value_t::number_float`    |
| object                    | `value_t::object`          |
| array                     | `value_t::array`           |
| binary                    | `value_t::binary`          |
| discarded                 | `value_t::discarded`       |

## Exception safety

No-throw guarantee: this member function never throws exceptions.

## Complexity

Constant.

## Examples

??? example

    The following code exemplifies `operator value_t()` for all JSON types.
    
    ```cpp
    #include <iostream>
    #include <nlohmann/json.hpp>
    
    using json = nlohmann::json;
    
    int main()
    {
        // create JSON values
        json j_null;
        json j_boolean = true;
        json j_number_integer = -17;
        json j_number_unsigned = 42u;
        json j_number_float = 23.42;
        json j_object = {{"one", 1}, {"two", 2}};
        json j_array = {1, 2, 4, 8, 16};
        json j_string = "Hello, world";
    
        // call operator value_t()
        json::value_t t_null = j_null;
        json::value_t t_boolean = j_boolean;
        json::value_t t_number_integer = j_number_integer;
        json::value_t t_number_unsigned = j_number_unsigned;
        json::value_t t_number_float = j_number_float;
        json::value_t t_object = j_object;
        json::value_t t_array = j_array;
        json::value_t t_string = j_string;
    
        // print types
        std::cout << std::boolalpha;
        std::cout << (t_null == json::value_t::null) << '\n';
        std::cout << (t_boolean == json::value_t::boolean) << '\n';
        std::cout << (t_number_integer == json::value_t::number_integer) << '\n';
        std::cout << (t_number_unsigned == json::value_t::number_unsigned) << '\n';
        std::cout << (t_number_float == json::value_t::number_float) << '\n';
        std::cout << (t_object == json::value_t::object) << '\n';
        std::cout << (t_array == json::value_t::array) << '\n';
        std::cout << (t_string == json::value_t::string) << '\n';
    }
    
    ```
    
    Output:
    
    ```json
    true
    true
    true
    true
    true
    true
    true
    true
    
    ```

## See also

- [type](type.md) named member function equivalent to this implicit conversion operator
- [value_t](value_t.md) the enumeration of JSON types

## Version history

- Added in version 1.0.0.
- Added unsigned integer type in version 2.0.0.
- Added binary type in version 3.8.0.