acorn-walk vs estree-walker
JavaScript AST (Abstract Syntax Tree) Traversal Comparison
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What's JavaScript AST (Abstract Syntax Tree) Traversal?

JavaScript AST (Abstract Syntax Tree) Traversal libraries are tools that allow developers to navigate and manipulate the structure of JavaScript code programmatically. These libraries parse JavaScript code into a tree-like structure, where each node represents a part of the code (such as a variable, function, or expression). By traversing this tree, developers can analyze, transform, or generate code, making these libraries essential for tasks like linting, code formatting, and building compilers or transpilers. acorn-walk is a simple and efficient AST walker for Acorn, a fast JavaScript parser, while estree-walker is a more flexible walker designed for ESTree-compliant ASTs, supporting various traversal patterns and allowing for easier integration with other tools in the JavaScript ecosystem.

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acorn-walk52,902,40711,02252.3 kB1710 months agoMIT
estree-walker51,456,95641417.6 kB113 years agoMIT
Feature Comparison: acorn-walk vs estree-walker

AST Compatibility

  • acorn-walk:

    acorn-walk is specifically designed for the AST generated by the Acorn parser. It is optimized for this particular AST structure, making it highly efficient for projects that use Acorn for parsing.

  • estree-walker:

    estree-walker is designed to work with ESTree-compliant ASTs, which are a standardized format for representing JavaScript code. This makes estree-walker more versatile and compatible with a wider range of parsers and tools that adhere to the ESTree specification.

Traversal Flexibility

  • acorn-walk:

    acorn-walk provides a simple and straightforward API for traversing the AST. It supports depth-first and breadth-first traversal but lacks advanced features like custom node handling or asynchronous traversal.

  • estree-walker:

    estree-walker offers more flexibility in how traversal is performed. It supports custom walkers, allows for asynchronous traversal, and provides more control over the traversal process, making it suitable for complex use cases.

Integration with Other Tools

  • acorn-walk:

    acorn-walk is tightly integrated with the Acorn parser, making it a natural choice for projects that use Acorn. However, its integration with other tools and parsers is limited due to its specificity.

  • estree-walker:

    estree-walker is designed to be compatible with other ESTree-based tools and libraries, making it a better choice for projects that require interoperability with multiple parsers and tools in the JavaScript ecosystem.

Performance

  • acorn-walk:

    acorn-walk is lightweight and performs well for most traversal tasks, especially when working with smaller to medium-sized ASTs generated by Acorn.

  • estree-walker:

    estree-walker is also performant, but its flexibility and additional features may introduce some overhead. However, it is designed to handle large ASTs efficiently, making it suitable for more complex traversal tasks.

Ease of Use: Code Examples

  • acorn-walk:

    Simple AST Traversal with acorn-walk

    import { parse } from 'acorn';
import { simple } from 'acorn-walk';

const code = 'const x = 10;';
const ast = parse(code);

simple(ast, {
  VariableDeclaration(node) {
    console.log('Found a variable declaration:', node);
  },
});
  • estree-walker:

    Flexible AST Traversal with estree-walker

    import { walk } from 'estree-walker';

const ast = {
  type: 'Program',
  body: [
    { type: 'VariableDeclaration', declarations: [], kind: 'const' },
  ],
};

walk(ast, {
  enter(node) {
    console.log('Entering node:', node.type);
  },
  leave(node) {
    console.log('Leaving node:', node.type);
  },
});
How to Choose: acorn-walk vs estree-walker
  • acorn-walk:

    Choose acorn-walk if you are working with the Acorn parser and need a lightweight, straightforward solution for traversing its AST. It is ideal for projects that require simple walking functionality without additional complexity.

  • estree-walker:

    Choose estree-walker if you need a more flexible and feature-rich walking solution that supports ESTree-compliant ASTs. It is suitable for projects that require advanced traversal capabilities, such as custom node handling, and is designed to work well with other ESTree-based tools.

Similar Npm Packages to acorn-walk

acorn-walk is a utility library designed to work with the Acorn parser, which is a small, fast JavaScript parser written in JavaScript. Acorn-walk allows developers to traverse and manipulate the abstract syntax tree (AST) generated by Acorn, making it easier to analyze and transform JavaScript code. This library is particularly useful for building tools like linters, code analyzers, and transpilers.

While acorn-walk is a powerful tool for working with JavaScript ASTs, there are several alternatives that provide similar functionality. Here are a few notable options:

  • acorn is the underlying parser that acorn-walk relies on. It is a fast and efficient JavaScript parser that generates an AST from JavaScript code. While acorn itself does not provide traversal capabilities, it serves as the foundation for acorn-walk and other libraries that build upon it. If you need a lightweight and performant parser for JavaScript, acorn is an excellent choice.
  • esprima is another popular JavaScript parser that generates an AST. It is known for its compliance with the ECMAScript specification and provides a robust parsing solution for JavaScript code. Esprima also allows for easy traversal of the generated AST, making it a suitable alternative for developers looking for a comprehensive parsing and traversal solution.
  • estraverse is a library specifically designed for traversing and manipulating ASTs in JavaScript. It works with ASTs generated by various parsers, including Acorn and Esprima. Estraverse provides a simple API for walking through the tree and applying transformations, making it a great choice for developers who need to analyze or modify JavaScript code at the AST level.
  • recast is a powerful tool for working with JavaScript code that allows for parsing, transforming, and printing code. It uses the Babel parser under the hood and provides a rich API for manipulating the AST. Recast is particularly useful for code transformations and refactoring, making it a strong alternative for developers looking to work with JavaScript code in a more comprehensive manner.

To see how these packages compare, check out the comparison: Comparing acorn vs acorn-walk vs esprima vs estraverse vs recast.

Similar Npm Packages to estree-walker

estree-walker is a library designed for traversing and transforming Abstract Syntax Trees (ASTs) that conform to the ESTree specification. It provides a simple and efficient way to walk through the nodes of an AST, allowing developers to perform various operations such as analysis, transformation, or code generation. While estree-walker is a powerful tool for working with ESTree-compliant ASTs, there are several alternatives in the JavaScript ecosystem that offer similar functionalities. Here are a few notable alternatives:

  • acorn-walk is a utility for traversing the AST generated by the Acorn parser. It provides a straightforward API for walking through the nodes of the AST, allowing developers to easily implement custom transformations or analyses. If you are using Acorn for parsing JavaScript code and need a simple way to traverse its AST, acorn-walk is a solid choice.
  • esprima is a high-performance, standard-compliant JavaScript parser that produces an AST. While esprima itself is primarily focused on parsing, it can be used in conjunction with other libraries to traverse and manipulate the resulting AST. If you need a robust parser along with the ability to work with the AST, esprima is a great option.
  • estraverse is a library specifically designed for traversing ESTree-compliant ASTs. It provides a flexible API for walking through nodes and allows for easy manipulation of the AST. If you are looking for a dedicated solution for traversing ESTree ASTs, estraverse is a well-established choice that offers a range of features for node manipulation.
  • recast is a powerful library for working with JavaScript code that allows for parsing, transforming, and printing code. It uses an AST to represent the code structure and provides a rich API for manipulating it. If you need to perform complex transformations on JavaScript code while preserving its original formatting, recast is an excellent option.

To see how estree-walker compares with acorn-walk, esprima, estraverse, and recast, check out the comparison: Comparing acorn-walk vs esprima vs estraverse vs estree-walker vs recast.

README for acorn-walk

Acorn AST walker

An abstract syntax tree walker for the ESTree format.

Community

Acorn is open source software released under an MIT license.

You are welcome to report bugs or create pull requests on github.

Installation

The easiest way to install acorn is from npm:

npm install acorn-walk

Alternately, you can download the source and build acorn yourself:

git clone https://github.com/acornjs/acorn.git
cd acorn
npm install

Interface

An algorithm for recursing through a syntax tree is stored as an object, with a property for each tree node type holding a function that will recurse through such a node. There are several ways to run such a walker.

simple(node, visitors, base, state) does a 'simple' walk over a tree. node should be the AST node to walk, and visitors an object with properties whose names correspond to node types in the ESTree spec. The properties should contain functions that will be called with the node object and, if applicable the state at that point. The last two arguments are optional. base is a walker algorithm, and state is a start state. The default walker will simply visit all statements and expressions and not produce a meaningful state. (An example of a use of state is to track scope at each point in the tree.)

const acorn = require("acorn")
const walk = require("acorn-walk")

walk.simple(acorn.parse("let x = 10"), {
  Literal(node) {
    console.log(`Found a literal: ${node.value}`)
  }
})

ancestor(node, visitors, base, state) does a 'simple' walk over a tree, building up an array of ancestor nodes (including the current node) and passing the array to the callbacks as a third parameter.

const acorn = require("acorn")
const walk = require("acorn-walk")

walk.ancestor(acorn.parse("foo('hi')"), {
  Literal(_node, _state, ancestors) {
    console.log("This literal's ancestors are:", ancestors.map(n => n.type))
  }
})

recursive(node, state, functions, base) does a 'recursive' walk, where the walker functions are responsible for continuing the walk on the child nodes of their target node. state is the start state, and functions should contain an object that maps node types to walker functions. Such functions are called with (node, state, c) arguments, and can cause the walk to continue on a sub-node by calling the c argument on it with (node, state) arguments. The optional base argument provides the fallback walker functions for node types that aren't handled in the functions object. If not given, the default walkers will be used.

make(functions, base) builds a new walker object by using the walker functions in functions and filling in the missing ones by taking defaults from base.

full(node, callback, base, state) does a 'full' walk over a tree, calling the callback with the arguments (node, state, type) for each node

fullAncestor(node, callback, base, state) does a 'full' walk over a tree, building up an array of ancestor nodes (including the current node) and passing the array to the callbacks as a third parameter.

const acorn = require("acorn")
const walk = require("acorn-walk")

walk.full(acorn.parse("1 + 1"), node => {
  console.log(`There's a ${node.type} node at ${node.ch}`)
})

findNodeAt(node, start, end, test, base, state) tries to locate a node in a tree at the given start and/or end offsets, which satisfies the predicate test. start and end can be either null (as wildcard) or a number. test may be a string (indicating a node type) or a function that takes (nodeType, node) arguments and returns a boolean indicating whether this node is interesting. base and state are optional, and can be used to specify a custom walker. Nodes are tested from inner to outer, so if two nodes match the boundaries, the inner one will be preferred.

findNodeAround(node, pos, test, base, state) is a lot like findNodeAt, but will match any node that exists 'around' (spanning) the given position.

findNodeAfter(node, pos, test, base, state) is similar to findNodeAround, but will match all nodes after the given position (testing outer nodes before inner nodes).

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