Returns a new object with the results of passing the value (first argument!) and key (second argument) of each property to the given function.
In other words, the returned object associates the existing keys with new values as returned by the given function.
Returns a new object with the results of passing the value (first argument!) and key (second argument) of each property to the given function. In other words, the returned object associates the existing keys with new values as returned by the given function.