[#nlohmann-basic_json-0c-contains-03]
= xref:nlohmann.adoc[nlohmann]::xref:nlohmann/basic_json-0c.adoc[basic_json]::contains
:relfileprefix: ../../
:mrdocs:

check the existence of an element in a JSON object

== Synopsis

Declared in `<nlohmann/json.hpp>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class KeyType>
requires detail::is_usable_as_basic_json_key_type<basic_json_t, KeyType>::value
bool
contains(KeyType&& key) const;
----

== Return Value

whether the JSON object contains an element with the given key

== Parameters

[cols="1,4"]
|===
| Name| Description
| *key*
| key to check for
|===


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