estree-util-scope

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

Contents

* What is this?
* When should I use this?
* Install
* Use
* API
* Scope
* Visitors
* createVisitors()
* Examples
* Example: just the top scope
* Compatibility
* Related
* Security
* Contribute
* 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

`

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

$3

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

$3

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

$3

Create state to track what’s defined.

###### Parameters

There are no parameters.

###### Returns

State (Visitors).

Examples

$3

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

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

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

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[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