JSONCollection[…] = … (gb.util.web)

Dim hJSONCollection As JSONCollection
Dim aVariant As Variant
hJSONCollection [ Key As String ] = aVariant

Associates a value with Key.

Contrary to the Collection class, you can associate a key with the NULL value.

Consequently:

To make the difference with a non-existent key, you have to use the Exist method.
To remove a value, you have to use the Remove method.