estree-util-visit

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[estree][] (and [esast][]) utility to visit nodes.

* What is this?
* When should I use this?
* Install
* Use
* API
* visit(tree, visitor|visitors)
* CONTINUE
* EXIT
* SKIP
* Action
* ActionTuple
* Index
* Visitor
* Visitors
* Types
* Compatibility
* Related
* Contribute
* License

What is this?

This package is a utility that helps you walk the tree.

When should I use this?

This package helps when dealing with JavaScript ASTs.
Use [unist-util-visit][unist-util-visit] for other unist ASTs.

Install

This package is [ESM only][esm].
In Node.js (version 16+), install with [npm][]:

``sh npm install estree-util-visit`

In Deno with [esm.sh][esmsh]:

`js import {visit} from 'https://esm.sh/estree-util-visit@2'`

In browsers with [esm.sh][esmsh]:

`html`

`Use`

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

const tree = parse( 'export function x() { console.log(1 + "2"); process.exit(3) }', {sourceType: 'module', ecmaVersion: 2020} )

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

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

Yields:

`txt 1 "2" 3`

`API`

This package exports the identifiers [CONTINUE][api-continue], [EXIT][api-exit], [SKIP][api-skip], and [visit][api-visit]. There is no default export.

`$3`

Visit nodes, with ancestral information.

This algorithm performs [depth-first][depth-first] [tree traversal][tree-traversal] in [preorder][preorder] (NLR) and/or [postorder][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][is] to check if a node matches, and then perform different operations.

###### Parameters

* tree ([Node][node]) — tree to traverse *visitor ([Visitor][api-visitor]) — same as passing{enter: visitor}*visitors ([Visitors][api-visitors]) — handle each node

###### Returns

Nothing (undefined).

`$3`

Continue traversing as normal (symbol).

`$3`

Stop traversing immediately (symbol).

`$3`

Do not traverse this node’s children (symbol).

`$3`

Union of the action types (TypeScript type).

###### Type

`ts type Action = typeof CONTINUE | typeof EXIT | typeof SKIP`

`$3`

List with one or two values, the first an action, the second an index (TypeScript type).

###### Type

`$3`

Move to the sibling at indexnext (after node itself is completely traversed), when moving in an array (TypeScript type).

Useful if mutating the tree, such as removing the node the visitor is currently on, or any of its previous siblings. Results less than 0 or greater than or equal tochildren.lengthstop traversing the parent.

###### Type

`ts type Index = number`

`$3`

Handle a node (TypeScript type).

Visitors are free to transform node. They can also transform the parent of node (the last ofancestors).

Replacing node itself, if SKIPis not returned, still causes its descendants to be walked (which is a bug).

When adding or removing previous siblings of node, the Visitorshould return a newIndex to specify the sibling to traverse after nodeis traversed. Adding or removing next siblings ofnodeis handled as expected without needing to return a newIndex.

###### Parameters

* node ([Node][node]) — found node *key (string or undefined) — field at whichnodelives in its parent (or where a list of nodes lives) *index (number or undefined) — index wherenode lives if parent[key]is an array *ancestors ([Array][node]) — ancestors ofnode

###### Returns

What to do next ([Action][api-action], [Index][api-index], or [ActionTuple][api-action-tuple], optional).

An Index is treated as a tuple of [CONTINUE, Index]. AnAction is treated as a tuple of [Action].

Passing a tuple back only makes sense if the Action is SKIP. When theAction is EXIT, that action can be returned. When theAction is CONTINUE, Index can be returned.

`$3`

Handle nodes when entering (preorder) and leaving (postorder) (TypeScript type).

###### Fields

* enter ([Visitor][api-visitor], optional) — handle nodes when entering (preorder) *leave ([Visitor][api-visitor], optional) — handle nodes when leaving (postorder)

`Types`

This package is fully typed with [TypeScript][]. It exports the additional types [Action][api-action], [ActionTuple][api-action-tuple], [Index][api-index], [Visitor][api-visitor], and [Visitors][api-visitors].

`Compatibility`

Projects maintained by the unified collective are compatible with maintained versions of Node.js.

When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line,estree-util-visit@^2, compatible with Node.js 16.

`Related`

* unist-util-visit— walk any unist tree

`Contribute`

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

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

License

[MIT][license] © [Titus Wormer][author]

[build-badge]: https://github.com/syntax-tree/estree-util-visit/workflows/main/badge.svg

[build]: https://github.com/syntax-tree/estree-util-visit/actions

[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/estree-util-visit.svg

[coverage]: https://codecov.io/github/syntax-tree/estree-util-visit

[downloads-badge]: https://img.shields.io/npm/dm/estree-util-visit.svg

[downloads]: https://www.npmjs.com/package/estree-util-visit

[size-badge]: https://img.shields.io/badge/dynamic/json?label=minzipped%20size&query=$.size.compressedSize&url=https://deno.bundlejs.com/?q=estree-util-visit

[size]: https://bundlejs.com/?q=estree-util-visit

[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg

[backers-badge]: https://opencollective.com/unified/backers/badge.svg

[collective]: https://opencollective.com/unified

[chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg

[chat]: https://github.com/syntax-tree/unist/discussions

[npm]: https://docs.npmjs.com/cli/install

[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c

[esmsh]: https://esm.sh

[typescript]: https://www.typescriptlang.org

[license]: license

[author]: https://wooorm.com

[health]: https://github.com/syntax-tree/.github

[contributing]: https://github.com/syntax-tree/.github/blob/main/contributing.md

[support]: https://github.com/syntax-tree/.github/blob/main/support.md

[coc]: https://github.com/syntax-tree/.github/blob/main/code-of-conduct.md

[esast]: https://github.com/syntax-tree/esast

[estree]: https://github.com/estree/estree

[depth-first]: https://github.com/syntax-tree/unist#depth-first-traversal

[tree-traversal]: https://github.com/syntax-tree/unist#tree-traversal

[preorder]: https://github.com/syntax-tree/unist#preorder

[postorder]: https://github.com/syntax-tree/unist#postorder

[is]: https://github.com/syntax-tree/unist-util-is

[node]: https://github.com/syntax-tree/esast#node

[unist-util-visit]: https://github.com/syntax-tree/unist-util-visit

[api-continue]: #continue

[api-action]: #action

[api-action-tuple]: #actiontuple

[api-exit]: #exit

[api-index]: #index

[api-skip]: #skip

[api-visit]: #visittree-visitorvisitors

[api-visitor]: #visitor

[api-visitors]: #visitors

estree-util-visit

[estree][] (and [esast][]) utility to visit nodes.

What is this?

This package is a utility that helps you walk the tree.

When should I use this?

This package helps when dealing with JavaScript ASTs.
Use [unist-util-visit][unist-util-visit] for other unist ASTs.

Install

This package is [ESM only][esm].
In Node.js (version 16+), install with [npm][]:

``sh npm install estree-util-visit`

In Deno with [esm.sh][esmsh]:

`js import {visit} from 'https://esm.sh/estree-util-visit@2'`

In browsers with [esm.sh][esmsh]:

`html`

`Use`

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

const tree = parse( 'export function x() { console.log(1 + "2"); process.exit(3) }', {sourceType: 'module', ecmaVersion: 2020} )

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

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

Yields:

`txt 1 "2" 3`

`API`

This package exports the identifiers [CONTINUE][api-continue], [EXIT][api-exit], [SKIP][api-skip], and [visit][api-visit]. There is no default export.

`$3`

Visit nodes, with ancestral information.

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

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

###### Parameters

* tree ([Node][node]) — tree to traverse *visitor ([Visitor][api-visitor]) — same as passing{enter: visitor}*visitors ([Visitors][api-visitors]) — handle each node

###### Returns

Nothing (undefined).

`$3`

Continue traversing as normal (symbol).

`$3`

Stop traversing immediately (symbol).

`$3`

Do not traverse this node’s children (symbol).

`$3`

Union of the action types (TypeScript type).

###### Type

`ts type Action = typeof CONTINUE | typeof EXIT | typeof SKIP`

`$3`

List with one or two values, the first an action, the second an index (TypeScript type).

###### Type

`$3`

Move to the sibling at indexnext (after node itself is completely traversed), when moving in an array (TypeScript type).

###### Type

`ts type Index = number`

`$3`

Handle a node (TypeScript type).

Visitors are free to transform node. They can also transform the parent of node (the last ofancestors).

Replacing node itself, if SKIPis not returned, still causes its descendants to be walked (which is a bug).

###### Parameters

###### Returns

What to do next ([Action][api-action], [Index][api-index], or [ActionTuple][api-action-tuple], optional).

An Index is treated as a tuple of [CONTINUE, Index]. AnAction is treated as a tuple of [Action].

Passing a tuple back only makes sense if the Action is SKIP. When theAction is EXIT, that action can be returned. When theAction is CONTINUE, Index can be returned.

`$3`

Handle nodes when entering (preorder) and leaving (postorder) (TypeScript type).

###### Fields

* enter ([Visitor][api-visitor], optional) — handle nodes when entering (preorder) *leave ([Visitor][api-visitor], optional) — handle nodes when leaving (postorder)

`Types`

`Compatibility`

Projects maintained by the unified collective are compatible with maintained versions of Node.js.

When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line,estree-util-visit@^2, compatible with Node.js 16.

`Related`

* unist-util-visit— walk any unist tree

`Contribute`

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

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

License

[build-badge]: https://github.com/syntax-tree/estree-util-visit/workflows/main/badge.svg

[build]: https://github.com/syntax-tree/estree-util-visit/actions

[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/estree-util-visit.svg

[coverage]: https://codecov.io/github/syntax-tree/estree-util-visit

[downloads-badge]: https://img.shields.io/npm/dm/estree-util-visit.svg

[downloads]: https://www.npmjs.com/package/estree-util-visit

[size-badge]: https://img.shields.io/badge/dynamic/json?label=minzipped%20size&query=$.size.compressedSize&url=https://deno.bundlejs.com/?q=estree-util-visit

[size]: https://bundlejs.com/?q=estree-util-visit

[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg

[backers-badge]: https://opencollective.com/unified/backers/badge.svg

[collective]: https://opencollective.com/unified

[chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg

[chat]: https://github.com/syntax-tree/unist/discussions

[npm]: https://docs.npmjs.com/cli/install

[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c

[esmsh]: https://esm.sh

[typescript]: https://www.typescriptlang.org

[license]: license

[author]: https://wooorm.com

[health]: https://github.com/syntax-tree/.github

[contributing]: https://github.com/syntax-tree/.github/blob/main/contributing.md

[support]: https://github.com/syntax-tree/.github/blob/main/support.md

[coc]: https://github.com/syntax-tree/.github/blob/main/code-of-conduct.md

[esast]: https://github.com/syntax-tree/esast

[estree]: https://github.com/estree/estree

[depth-first]: https://github.com/syntax-tree/unist#depth-first-traversal

[tree-traversal]: https://github.com/syntax-tree/unist#tree-traversal

[preorder]: https://github.com/syntax-tree/unist#preorder

[postorder]: https://github.com/syntax-tree/unist#postorder

[is]: https://github.com/syntax-tree/unist-util-is

[node]: https://github.com/syntax-tree/esast#node

[unist-util-visit]: https://github.com/syntax-tree/unist-util-visit

[api-continue]: #continue

[api-action]: #action

[api-action-tuple]: #actiontuple

[api-exit]: #exit

[api-index]: #index

[api-skip]: #skip

[api-visit]: #visittree-visitorvisitors

[api-visitor]: #visitor

[api-visitors]: #visitors

estree-util-visit

estree-util-visit

Contents

What is this?

When should I use this?

Install

Use

API

$3

$3

$3

$3

$3

$3

$3

$3

$3

Types

Compatibility

Related

Contribute

License

estree-util-visit

estree-util-visit

Contents

What is this?

When should I use this?

Install

Use

API

$3

$3

$3

$3

$3

$3

$3

$3

$3

Types

Compatibility

Related

Contribute

License

`Use`

`API`

`$3`

`$3`

`$3`

`$3`

`$3`

`$3`

`$3`

`$3`

`$3`

`Types`

`Compatibility`

`Related`

`Contribute`

`Use`

`API`

`$3`

`$3`

`$3`

`$3`

`$3`

`$3`

`$3`

`$3`

`$3`

`Types`

`Compatibility`

`Related`

`Contribute`