A developer with 4 years of experience what at-least he/she should be knowing?

This is more opinion based, a developer having 4 year experience in JavaScript / Frontend / Backend, what atleast he/she should be knowing/nice to have/should target next?

The reason for this answer is learning is different from person to person and every field/stack has its own responsibility. Getting opinion from other developers it help each other to expand ourselves and upgrade our skills.

Thanks