Dynamically typed languages usually treat undefined values explicitly when possible.
JavaScript isn't even special compared to other dynamically typed language.
The fundamental building block of Coherence is the dynamically typed mutable tree.
Scheme represents its code and data as nested lists of dynamically typed elements.
However, historically, if the type of a value is known only at run-time; these languages are dynamically typed.
Most dynamic languages are also dynamically typed, but not all are.
In dynamically typed languages such as Python, it is values, not variables, which carry type.
Factor is a dynamically typed, functional and object-oriented programming language.
For example, Erlang is dynamically typed but has static name resolution.
This adds flexibility to columns, especially when bound to a dynamically typed scripting language.