|struct||The struct to check|
|string||The key (i.e. struct content) to begin search from|
Returns the name of the previous key in the given struct, as a string. Search will begin from the given key (for example, as returned by
If the struct is empty or no further key exists,
undefined will be returned instead.
Note that because structs are a non-ordered data format, data may be returned in a different order than originally declared in code. Changes to the struct may also change the order in which data is returned with this function.