Created empty() (markdown)

empty().md

@@ -0,0 +1,56 @@
+# nlohmann::basicjson::empty
+
+```cpp
+bool empty() const;
+```
+
+## Description
+
+Checks if a JSON value has no elements, i.e. whether `begin() == end()`. The return value depends on the different value types and is defined as follows:
+
+| Value type | return value          |
+| ---------- | --------------------- |
+| null       | `true`                |
+| number     | `false`               |
+| boolean    | `false`               |
+| string     | `false`               |
+| array      | `ArrayType::empty()`  |
+| object     | `ObjectType::empty()` |
+
+## Parameter
+
+None.
+
+## Complexity
+
+Constant, as long as `ArrayType` and `ObjectType` satisfy the [Container concept](http://en.cppreference.com/w/cpp/concept/Container).
+
+## Exceptions
+
+None. The function's noexcept-specification is `noexcept`.
+
+## Example
+
+The following code uses empty to check if a `nlohmann::json` contains any elements:
+
+```cpp
+#include <iostream>
+#include <json.hpp>
+ 
+int main()
+{
+    nlohmann::json numbers;
+    std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n';
+ 
+    numbers.push_back(42);
+    numbers.push_back(13317); 
+    std::cout << "After adding elements, numbers.empty(): " << numbers.empty() << '\n';
+}
+```
+
+Output:
+
+```
+Initially, numbers.empty(): 1
+After adding elements, numbers.empty(): 0
+```