Functional Logic & Control Flow
Variable/identifier shadowing
Last updated: 4 Mar 2026
Definition
A local identifier hides an outer one, leading to reads/writes on the wrong variable.
How to fix Variable/identifier shadowing?
Enable linter rules (no-shadow); rename conflicting vars; reduce scope; prefer small functions to avoid ambiguous contexts
Symptoms
Observable signs that may indicate Variable/identifier shadowing:
- Assignments have no effect outside block scope.
- Unexpected value read due to inner variable masking outer one.
- Linters warn about shadowed variables.
Example Errors:
- ESLint: 'result' is already declared in the upper scope.
- Shadowed variable 'config'
- TypeScript: Block-scoped variable used before declaration