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# nlohmann::basic_json::type_name

    const char* type_name() const noexcept;

Returns the type name as string to be used in error messages -- usually to indicate that a function was called on a wrong JSON type.

## Return value

a string representation of the type (`value_t`):

Value type | return value
--- | ---
`null` | `"null"`
boolean | `"boolean"`
string | `"string"`
number (integer, unsigned integer, floating-point) | `"number"`
object | `"object"`
array | `"array"`
binary | `"binary"`
discarded | `"discarded"`

## Exception safety

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

## Complexity

Constant.

## Examples

Example

The following code exemplifies `type_name()` 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 type_name()
        std::cout << j_null << " is a " << j_null.type_name() << '\n';
        std::cout << j_boolean << " is a " << j_boolean.type_name() << '\n';
        std::cout << j_number_integer << " is a " << j_number_integer.type_name() << '\n';
        std::cout << j_number_unsigned << " is a " << j_number_unsigned.type_name() << '\n';
        std::cout << j_number_float << " is a " << j_number_float.type_name() << '\n';
        std::cout << j_object << " is an " << j_object.type_name() << '\n';
        std::cout << j_array << " is an " << j_array.type_name() << '\n';
        std::cout << j_string << " is a " << j_string.type_name() << '\n';
    }

Output:

    null is a null
    true is a boolean
    -17 is a number
    42 is a number
    23.42 is a number
    {"one":1,"two":2} is an object
    [1,2,4,8,16] is an array
    "Hello, world" is a string

## Version history

- Added in version 1.0.0.
- Part of the public API version since 2.1.0.
- Changed return value to `const char*` and added `noexcept` in version 3.0.0.
- Added support for binary type in version 3.8.0.

Last update: May 1, 2022
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