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https://github.com/syntax-tree/esast-util-from-js

estree (and esast) utility to parse from JavaScript
https://github.com/syntax-tree/esast-util-from-js

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estree (and esast) utility to parse from JavaScript

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README 

        
# esast-util-from-js



[![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]



[esast][] (and [estree][]) utility to parse trees from JavaScript.



## Contents



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

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

*   [Install](#install)

*   [Use](#use)

*   [API](#api)

    *   [`fromJs(value[, options])`](#fromjsvalue-options)

    *   [`Options`](#options)

    *   [`Plugin`](#plugin)

    *   [`Value`](#value)

    *   [`Version`](#version-1)

*   [Types](#types)

*   [Compatibility](#compatibility)

*   [Contribute](#contribute)

*   [License](#license)



## What is this?



This package is a utility that turns a string of JavaScript into an esast

(estree with some extra cleanliness) syntax tree.



## When should I use this?



You can use this utility when you want to deal with ASTs of JavaScript

combined with other [unist][] and [`vfile`][vfile] things.

You can use [`acorn`][acorn] itself if you don’t care about unified.



The utility [`estree-util-to-js`][estree-util-to-js] does the inverse of this

utility.

It turns the tree into a string of JavaScript.



## Install



This package is [ESM only][esm].

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



```sh

npm install esast-util-from-js

```



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



```js

import {fromJs} from 'https://esm.sh/esast-util-from-js@2'

```



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



```html



  import {fromJs} from 'https://esm.sh/esast-util-from-js@2?bundle'



```



## Use



```js

import fs from 'node:fs/promises'

import {fromJs} from 'esast-util-from-js'



const tree = fromJs(await fs.readFile('example.js'), {module: true})



console.log(tree)

```



Yields:



```js

{

  type: 'Program',

  body: [

    {

      type: 'ImportDeclaration',

      specifiers: [Array],

      source: [Object],

      position: [Object]

    },

    {

      type: 'ImportDeclaration',

      specifiers: [Array],

      source: [Object],

      position: [Object]

    },

    {

      type: 'VariableDeclaration',

      declarations: [Array],

      kind: 'const',

      position: [Object]

    },

    {

      type: 'ExpressionStatement',

      expression: [Object],

      position: [Object]

    }

  ],

  sourceType: 'module',

  comments: [],

  position: {

    start: {line: 1, column: 1, offset: 0},

    end: {line: 7, column: 1, offset: 157}

  }

}

```



## API



This package exports the identifier [`fromJs`][api-from-js].

There is no default export.



### `fromJs(value[, options])`



Parse JavaScript to an esast.



###### Parameters



*   `value` ([`Value`][api-value])

    — serialized JavaScript to parse

*   `options` ([`Options`][api-options], optional)

    — configuration



###### Returns



Tree ([`Node`][node]).



###### Throws



When the JavaScript cannot be parsed with `acorn`, a

[`VFileMessage`][vfile-message] is thrown.



This can for example happen when passing modern syntax (you could maybe use a

newer `version`, or it might be that the syntax is not yet supported), or just

otherwise invalid JavaScript (you might need a plugin).



### `Options`



Configuration (TypeScript type).



##### Fields



###### `version`



JavaScript version ([`Version`][api-version], default: `'latest'`).



When a number, must be a year in the range `2015` and `2023` (both including).

`'latest'` is the same as passing the latest supported year.



> ☢️ **Danger**: `'latest'` is a sliding thing, you could consider it as

> breaking semver.

> Pass an actual year to lock that down.



###### `module`



Whether this is a module (ESM) or a script (`boolean`, default: `false`).



###### `allowReturnOutsideFunction`



Whether a return statement is allowed in the top scope (`boolean`, default:

`false`).



###### `allowImportExportEverywhere`



Whether import/export statements are allowed in the every scope (`boolean`,

default: `false`).



###### `allowAwaitOutsideFunction`



Whether `await` is allowed in the top scope (`boolean`, default: depends).

Defaults to `version >= 2022`.



###### `allowSuperOutsideMethod`



Whether `super` is allowed outside methods (`boolean`, default: `false`).



###### `allowHashBang`



Whether a shell hasbang is allowed (`boolean`, default: `false`).



###### `plugins`



List of acorn plugins ([`Array`][api-plugin], default: `[]`).

Examples are [`acorn-jsx`][acorn-jsx] and [`acorn-stage3`][acorn-stage3].



### `Plugin`



Acorn plugin (TypeScript type).



###### Type



```ts

type Plugin = (Parser: ParserClass) => ParserClass

```



### `Value`



Input value (TypeScript type).



When a typed array, must be UTF-8.



###### Type



```ts

type Value = Uint8Array | string

```



### `Version`



JavaScript version (TypeScript type).



`'latest'` is equivalent to the latest supported year.



###### Type



```ts

type Version = 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | 'latest'

```



## Types



This package is fully typed with [TypeScript][].

It exports the additional types [`Options`][api-options],

[`Plugin`][api-plugin],

[`Value`][api-value], and

[`Version`][api-version].



## 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, `esast-util-from-js@^2`,

compatible with Node.js 16.



## 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/esast-util-from-js/workflows/main/badge.svg



[build]: https://github.com/syntax-tree/esast-util-from-js/actions



[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/esast-util-from-js.svg



[coverage]: https://codecov.io/github/syntax-tree/esast-util-from-js



[downloads-badge]: https://img.shields.io/npm/dm/esast-util-from-js.svg



[downloads]: https://www.npmjs.com/package/esast-util-from-js



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



[size]: https://bundlejs.com/?q=esast-util-from-js



[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



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



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



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



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



[acorn]: https://github.com/acornjs/acorn



[acorn-jsx]: https://github.com/acornjs/acorn-jsx



[acorn-stage3]: https://github.com/acornjs/acorn-stage3



[estree-util-to-js]: https://github.com/syntax-tree/estree-util-to-js



[vfile-message]: https://github.com/vfile/vfile-message



[api-from-js]: #fromjsvalue-options



[api-options]: #options



[api-plugin]: #plugin



[api-value]: #value



[api-version]: #version-1