ReadonlyallowIf an object does not pass any of the rules, if this is true the reference will be copied. If false (default), a MergeReferenceError will be thrown. This only applies to objects, not functions or primitives.
ReadonlyrulesThe first clone rule that matches will be used.
If no rules match, the value will be copied by reference unless allowReferenceCopy is
false (default), in which case, a MergeReferenceError will be thrown.
Merge options defines the behavior for mergeDeep. See the defaultMergeOptions for defaults that will be used if any merge options are omitted.