JavaScript Environment: A Hash Map for Function Bindings

In computer science speak, we would call this object an environment. The value can just be the source code for the function if you want. In a real system, this would probably be optimized a bit more by breaking out the list of arguments into a separate data structure like an array. But on a high level, all that really matters is we store a mapping between the name of the function and its source code or some representation of that source code or definition.