has()

Syntax

has(container, address, ...addresses)
has(lvalue)

Similar to get, but returns boolean value indicating if the given index / key / path is in the container. Can be used to determine if get(...)==null means the element doesn’t exist, or the stored value for this address is null, and is cheaper to run than get.

Like get, it can accept multiple addresses for chains in nested containers. In this case has(foo:a:b) is equivalent to has(get(foo,a), b) or has(foo, a, b)