ESUtils

ESUtils is a foundational utility library for ECMAScript language tools, providing a 'utility box' for analyzing JavaScript Abstract Syntax Trees (ASTs), character codes, and keywords/reserved words based on specific ECMA262 editions. It offers functions to classify AST nodes (e.g., `isExpression`, `isStatement`), identify character types (e.g., `isDecimalDigit`, `isIdentifierStart`), and check for keywords (`isKeywordES5`, `isKeywordES6`). The current stable version is 2.0.3, released in 2018. Given its core utility nature, its API is highly stable, and its release cadence is low, typically for maintenance or specification updates. It serves as a building block for various JavaScript parsing, linting, and transformation projects, providing low-level, spec-compliant checks.