the name of the key you want to retrieve the value of
the value of the key or undefined if the key does not exist
Remove the key from the store if it exists.
the name of the key you want to remove
Add the key to the store, or update that key's value if it already exists.
the name of the key you want to create/update
the value you want to give the key you are creating/updating
Return the key's value, or null if the key does not exist.