convict
Featureful configuration management library for Node.js (nested structure, schema validation, etc.)
fast-tree-builder
Efficiently construct highly customizable bi-directional tree structures from iterable data.
anchor
High-level validation library for Node.js (used in Waterline)
jpv
Flexible and powerful JSON pattern validation library with support for complex, nested structures, array validation, and a wide range of validation patterns. Includes logical operators and strict/nullable types.