Checks if the container has no elements; that is, whether `begin() == end()`.
## Parameters
(none)
## Return value
`true` if the container is empty, `false` otherwise. Note that the JSON types string, number, and boolean are never empty, null values are always empty.
## Exceptions
`noexcept` specification: `noexcept`.
## Complexity
Constant (assuming types `ObjectType` and `ArrayType` satisfy the [Container](http://en.cppreference.com/w/cpp/concept/Container) concept).
## Example
The following code uses empty to check if a `json` container contains any elements: