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# nlohmann::basic_json::operator value_t

    constexpr operator value_t() const noexcept;

Return the type of the JSON value as a value from the `value_t` enumeration.

## Return value

the type of the JSON value

Value type | return value
--- | ---
`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.

    #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:

    true
    true
    true
    true
    true
    true
    true
    true

## 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.

Last update: May 1, 2022
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