unified

Project: syntax-tree/estree-util-visit

Package: estree-util-visit@1.0.0

  1. Dependencies: 0·Dependents: 1
  2. esast (and estree) utility to visit nodes
  1. util 130
  2. utility 126
  3. tree 44
  4. ast 32
  5. node 23
  6. javascript 17
  7. walk 8
  8. ecmascript 7
  9. visit 6
  10. estree 4
  11. esast 3
  12. recma 3
  13. esast-util 2

estree-util-visit

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esast (and estree) utility to visit nodes.

Similar to unist-util-visit. Basically the tiniest you can go (while being usable). Also has nice stack traces if something crashes.

Install

npm:

npm install estree-util-visit

Note that this package is ESM only: it must be imported instead of required.

Use

import {parse} from 'acorn'
import {visit} from 'estree-util-visit'

var tree = parse(
  'export function x() { console.log(1 + "2"); process.exit(3) }',
  {sourceType: 'module'}
)

visit(tree, function (node) {
  if (node.type === 'Literal') console.log(node.value)
})

// Both enter and leave:
// walk(tree, {
//   enter(node, field, index, parents) {},
//   leave(node, field, index, parents) {}
// })

Yields:

1
"2"
3

API

estree-util-visit exports the following identifiers: visit, EXIT, CONTINUE, and SKIP. There is no default export.

visit(tree, visitor|visitors)

Visit nodes (inclusive descendants of tree), with ancestral information.

This algorithm performs depth-first tree traversal in preorder (NLR) and/or postorder (LRN).

Compared to other estree walkers, this does not need a dictionary of which fields are nodes, because it ducktypes instead.

Walking the tree is an intensive task. Make use of the return values of the visitor(s) when possible. Instead of walking a tree multiple times, walk it once, use unist-util-is to check if a node matches, and then perform different operations.

Parameters

next? = visitor(node, key, index, ancestors)

Called when a node is found.

Visitors are free to transform node. They can also transform the parent of node (the last of ancestors). Replacing node itself, if SKIP is not returned, still causes its descendants to be walked. If adding or removing previous siblings of node, visitor should return a new index (number) to specify the sibling to traverse after node is traversed. Adding or removing next siblings of node is handled as expected without needing to return a new index.

Parameters
Returns

The return value can have the following forms:

action

An action can have the following values:

Contribute

See contributing.md in syntax-tree/.github for ways to get started. See support.md for ways to get help.

This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.

License

MIT © Titus Wormer