@typescript-eslint/visitor-keys

What is @typescript-eslint/visitor-keys?

The @typescript-eslint/visitor-keys package provides an enumeration of TypeScript ESTree AST node types and their respective visitor keys. It is primarily used in the context of ESLint plugins and custom rules development to traverse the AST (Abstract Syntax Tree) of TypeScript code and analyze or manipulate the code structure.

What are @typescript-eslint/visitor-keys's main functionalities?

AST Node Traversal

This code demonstrates how to use the visitor keys from the package to traverse an AST node and its children recursively. The `traverseAST` function takes a node and a visitor object that contains methods corresponding to node types. It uses the visitor keys to determine which properties of a node to traverse.

const visitorKeys = require('@typescript-eslint/visitor-keys');

function traverseAST(node, visitor) {
  if (visitor[node.type]) {
    visitor[node.type](node);
  }

  const keys = visitorKeys[node.type] || [];
  keys.forEach((key) => {
    const value = node[key];
    if (Array.isArray(value)) {
      value.forEach(child => traverseAST(child, visitor));
    } else if (value && typeof value === 'object') {
      traverseAST(value, visitor);
    }
  });
}

Other packages similar to @typescript-eslint/visitor-keys

eslint-visitor-keys

This package provides a list of visitor keys for traversing the AST of JavaScript code. It is similar to @typescript-eslint/visitor-keys but is tailored for JavaScript rather than TypeScript. It is used by ESLint to work with its own rules and plugins.

babel-types

While not a direct equivalent, babel-types is part of the Babel ecosystem and provides definitions for various AST node types, builders, and assertion methods. It can be used to traverse and manipulate ASTs for both JavaScript and TypeScript, offering a broader scope compared to @typescript-eslint/visitor-keys.

estraverse

Estraverse is a simple and flexible library for traversing and replacing nodes in an ECMAScript AST. It is not TypeScript-specific but can be used with JavaScript ASTs. It provides a similar traversal functionality but does not rely on a predefined set of visitor keys.

README

@typescript-eslint/visitor-keys

Visitor keys used to help traverse the TypeScript-ESTree AST.

✋ Internal Package

This is an internal package to the typescript-eslint monorepo. You likely don't want to use it directly.

👉 See https://typescript-eslint.io for docs on typescript-eslint.

Changelog

8.23.0 (2025-02-03)

🚀 Features

• eslint-plugin: [no-unnecessary-boolean-literal-compare] enforce strictNullChecks (#10712)
• types: add strict parent types for function-declaration, default-export and named-export nodes (#10685)

🩹 Fixes

• bump ts-api-utils to ^2.0.1 (#10761)
• deps: update eslint monorepo to v9.19.0 (#10752)
• eslint-plugin: [no-unnecessary-type-assertion] should report readonly class properties with a literal initializer (#10618)
• eslint-plugin: [switch-exhaustiveness-check] suggest with qualified name (#10697)
• eslint-plugin: [no-unnecessary-template-expression] allow interpolating type parameter in type context (#10739)
• eslint-plugin: [prefer-nullish-coalescing] fix missing return (#10732)
• eslint-plugin: [dot-notation] handle noPropertyAccessFromIndexSignature true (#10644)
• eslint-plugin: [no-restricted-imports] support regex option (#10699)
• eslint-plugin: [no-shadow] ignore declare variables in definition files shadowing global variables (#10710)

❤️ Thank You

• Josh Goldberg ✨
• Olivier Zalmanski @OlivierZal
• Ronen Amiel
• Ryan Poon @sopa301
• YeonJuan @yeonjuan
• Yukihiro Hasegawa @y-hsgw

You can read about our versioning strategy and releases on our website.