var-to-let-const
Convert var declarations to let or const based on reassignment analysis, preserving function-scoped behavior when variables are accessed outside block scope.
Supported Use Cases and Patterns
This codemod intelligently converts var declarations to modern ES6+ syntax:
- Basic conversions: Variables that are never reassigned become
const; variables that are reassigned becomelet - Update expressions: Handles
++,--,+=,-=, and other compound assignments - Loop variables: Correctly identifies variables in
for...inandfor...ofloops - Nested scopes: Analyzes variables independently within their respective scopes
- Variable shadowing: Handles variables with the same name in different scopes correctly
- Conditional assignments: Works with assignments inside
if,switch, and ternary expressions - Complex expressions: Preserves object property and array index assignments without affecting variable declarations
- TSX/React: Supports TypeScript and JSX syntax
- Uninitialized variables: Converts
var x;tolet x;(sinceconstrequires initialization) - Function-scoped preservation: Safely skips conversion when
varis accessed outside its block scope (preserving function-scoped behavior)
Example
Before:
After:
Enterprise Features
Enterprise customers get access to additional features and support:
- Sharding by codeowner or directory: Efficiently process large codebases by splitting work across teams or code ownership boundaries
- AI review and automated quality checks: Automated code review and quality assurance to ensure transformations maintain code quality and correctness
- Pre and post run hooks: Customize the codemod workflow with pre-run validation and post-run verification steps
- Priority support and updates: Get priority support for issues and early access to new features and improvements
- Team training and onboarding: Comprehensive training and onboarding resources to help your team effectively use and maintain codemods