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# nlohmann::basic_json::size

    size_type size() const noexcept;

Returns the number of elements in a JSON value.

## Return value

The return value depends on the different types and is defined as follows:

Value type | return value
--- | ---
null | `0`
boolean | `1`
string | `1`
number | `1`
binary | `1`
object | result of function object_t::size()
array | result of function array_t::size()

## Exception safety

No-throw guarantee: this function never throws exceptions.

## Complexity

Constant, as long as `array_t` and `object_t` satisfy the Container concept; that is, their `size()` functions have constant complexity.

## Notes

This function does not return the length of a string stored as JSON value -- it returns the number of elements in the JSON value which is `1` in the case of a string.

## Examples

Example

The following code calls `size()` on the different value 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_float = 23.42;
        json j_object = {{"one", 1}, {"two", 2}};
        json j_object_empty(json::value_t::object);
        json j_array = {1, 2, 4, 8, 16};
        json j_array_empty(json::value_t::array);
        json j_string = "Hello, world";

        // call size()
        std::cout << j_null.size() << '\n';
        std::cout << j_boolean.size() << '\n';
        std::cout << j_number_integer.size() << '\n';
        std::cout << j_number_float.size() << '\n';
        std::cout << j_object.size() << '\n';
        std::cout << j_object_empty.size() << '\n';
        std::cout << j_array.size() << '\n';
        std::cout << j_array_empty.size() << '\n';
        std::cout << j_string.size() << '\n';
    }

Output:

    0
    1
    1
    1
    2
    0
    5
    0
    1

## Version history

- Added in version 1.0.0.
- Extended to return `1` for binary types in version 3.8.0.

Last update: May 1, 2022
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