It can be tough for me to guess your intention. On one hand you're declaring that both a and b are public (no leading underscore of their names) so I should really theoretically be allowed to access/mutate (get/established) the two. But You then specify an express mutator only for a, https://smartworlddeveloper.co.in/smart-world-69-sector-69-gurgaon-a-new-benchmark-in-urban-luxury-living/