iterate-objects-safely

To safely iterate object keys and values in TypeScript, replace for...in loops with Object.entries. This avoids unsafe indexing with obj[k] and prevents prototype pollution risks by yielding values as unknown for type safety.

Using for...in loops causes unsafe indexing because it exposes string keys without narrow types, allowing unsafe obj[k] access. Structural typing permits extra properties, leading to potential prototype pollution risks during object iteration.

The best way to achieve precise narrow types when iterating known object properties is using explicit key lists (as const). This enforces a type-safe traversal pattern and guides correct handling of known versus unknown object shapes.

Prefer Map over plain objects for data storage when you need guaranteed type safety and want to avoid prototype-related pitfalls. Map provides stronger type safety for scenarios like config validation and heterogeneous data extraction.

To handle unknown object shapes during data transformation, use Object.entries to safely iterate keys as strings and values as unknown. This type-safe traversal pattern prevents errors when dealing with heterogeneous objects.