lebab

Lebab is an open-source tool designed to modernize JavaScript code by automatically transforming older syntax into modern ECMAScript 2015+ features. It achieves this by parsing source files into an abstract syntax tree and applying a series of transformation recipes, such as converting var declarations to let or const and turning traditional function expressions into arrow functions where appropriate. The set of transforms can be configured and combined, allowing selective modernization across a codebase.

The tool provides both a command-line interface and a programmatic API, enabling integration into build pipelines, editors, or pre-commit workflows. It aims to preserve the original program behavior while updating style and constructs, but users are advised to review results and run tests, since automated changes can affect scoping, binding, or runtime semantics in edge cases.

Lebab is community-driven and has been used to assist developers in migrating legacy JavaScript to more modern patterns. Its ecosystem includes a variety of transforms and plugins that extend its capabilities beyond the core conversions. While it can significantly reduce manual refactoring effort, it is typically complemented with manual verification to ensure correctness in complex codebases.

See also: JavaScript modernization, ES2015, modern JavaScript syntax.