ReadonlyallowIf an object does not pass any of the rules, if this is true (default) the reference will be copied. If false, a MergeReferenceError will be thrown. This only applies to objects, not functions or primitives.
ReadonlyrulesThe first merge rule where the second source object matches will be used.
Rules are only checked for values that have a typeof value of 'object'
If the first object does not pass the match, undefined will be passed to sourceA and the
rule is expected to return a clone of sourceB.
If no rules match, the value will be copied by reference unless allowReferenceCopy is
false, 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.