https://github.com/syntax-tree/estree-util-scope

Check what’s defined in an estree scope
https://github.com/syntax-tree/estree-util-scope

ecmascript estree javascript scope

Last synced: 2 months ago
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Check what’s defined in an estree scope

Host: GitHub
URL: https://github.com/syntax-tree/estree-util-scope
Owner: syntax-tree
License: mit
Created: 2024-08-29T14:48:29.000Z (about 1 year ago)
Default Branch: main
Last Pushed: 2024-09-19T09:59:14.000Z (about 1 year ago)
Last Synced: 2025-07-12T07:38:09.104Z (3 months ago)
Topics: ecmascript, estree, javascript, scope
Language: JavaScript
Homepage: https://unifiedjs.com
Size: 10.7 KB
Stars: 10
Watchers: 8
Forks: 0
Open Issues: 0
Metadata Files:
- Readme: readme.md
- License: license

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README

          # estree-util-scope

[![Build][build-badge]][build]

[![Coverage][coverage-badge]][coverage]

[![Downloads][downloads-badge]][downloads]

[![Size][size-badge]][size]

[![Sponsors][sponsors-badge]][collective]

[![Backers][backers-badge]][collective]

[![Chat][chat-badge]][chat]

[estree][] utility to check what’s defined in a scope.

## Contents

* [What is this?](#what-is-this)

* [When should I use this?](#when-should-i-use-this)

* [Install](#install)

* [Use](#use)

* [API](#api)

  * [`Scope`](#scope)

  * [`Visitors`](#visitors)

  * [`createVisitors()`](#createvisitors)

* [Examples](#examples)

  * [Example: just the top scope](#example-just-the-top-scope)

* [Compatibility](#compatibility)

* [Related](#related)

* [Security](#security)

* [Contribute](#contribute)

* [License](#license)

## What is this?

This package is a utility that tracks what’s defined in a scope.

## When should I use this?

If you are walking an estree already and want to find out what’s defined,

use this.

If you have more complex scoping needs,

see [`eslint-scope`][github-eslint-scope].

## Install

This package is [ESM only][esm].

In Node.js (version 16+), install with [npm][]:

```sh

npm install estree-util-scope

```

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

```js

import {createVisitors} from 'https://esm.sh/estree-util-scope@1'

```

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

```html

  import {createVisitors} from 'https://esm.sh/estree-util-scope@1?bundle'

```

## Use

Say we have the following `example.js`:

```js

/**

 * @import {Program} from 'estree'

 */

import {Parser} from 'acorn'

import {createVisitors} from 'estree-util-scope'

import {walk} from 'estree-walker'

const tree = /** @type {Program} */ (

  Parser.parse('import {a} from "b"; const c = 1', {

    ecmaVersion: 'latest',

    sourceType: 'module'

  })

)

const visitors = createVisitors()

walk(tree, {enter: visitors.enter, leave: visitors.exit})

console.log(visitors.scopes.at(-1))

```

…now running `node example.js` yields:

```js

{ block: false, defined: [ 'a', 'c' ] }

```

## API

### `Scope`

Scope.

###### Fields

* `block` (`boolean`)

  — whether this is a block scope or not;

  blocks are things made by `for` and `try` and `if`;

  non-blocks are functions and the top-level scope

* `defined` (`Array`)

  — identifiers that are defined in this scope

### `Visitors`

State to track what’s defined;

contains `enter`, `exit` callbacks you must call and `scopes`.

###### Fields

* `enter` (`(node: Node) => undefined`)

  — callback you must call when entering a node

* `exit` (`(node: Node) => undefined`)

  — callback you must call when exiting (leaving) a node

* `scopes` (`[topLevel: Scope, ...rest: Scope[]]`)

  — list of scopes;

  the first scope is the top-level scope;

  the last scope is the current scope

### `createVisitors()`

Create state to track what’s defined.

###### Parameters

There are no parameters.

###### Returns

State (`Visitors`).

## Examples

### Example: just the top scope

Sometimes, you only care about a top-scope.

Or otherwise want to skip a node.

How to do this depends on how you walk the tree.

With `estree-walker`,

you can skip by calling `this.skip`.

```js

/**

 * @import {Program} from 'estree'

 */

import {Parser} from 'acorn'

import {createVisitors} from 'estree-util-scope'

import {walk} from 'estree-walker'

const tree = /** @type {Program} */ (

  Parser.parse(

    'function a(b) { var c = 1; if (d) { var e = 2 } }; if (f) { var g = 2 }',

    {ecmaVersion: 'latest'}

  )

)

const visitors = createVisitors()

walk(tree, {

  enter(node) {

    visitors.enter(node)

    if (

      node.type === 'ArrowFunctionExpression' ||

      node.type === 'FunctionDeclaration' ||

      node.type === 'FunctionExpression'

    ) {

      this.skip()

      visitors.exit(node) // Call the exit handler manually.

    }

  },

  leave: visitors.exit

})

console.log(visitors.scopes.at(-1))

```

…yields:

```js

{ block: false, defined: [ 'a', 'g' ] }

```

## 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-scope@1`,

compatible with Node.js 16.

## Related

## Security

This package is safe.

## Contribute

See [`contributing.md` in `syntax-tree/.github`][contributing] 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-scope/workflows/main/badge.svg

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

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

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

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

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

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

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

[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

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

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

[esmsh]: https://esm.sh

[license]: license

[author]: https://wooorm.com

[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

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

[github-eslint-scope]: https://github.com/eslint/eslint-scope

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