# acorn-loose

> Error-tolerant ECMAScript parser

Latest version **8.5.2** (published 2025-07-01) · MIT license · 0 weekly downloads

## Install

```sh
npm install acorn-loose
pnpm add acorn-loose
yarn add acorn-loose
bun add acorn-loose
```

## Health

**Score 55/100 (C)** — status: stable.

Positive: has types; esm support; no vulnerabilities; high maintenance score; popular repo.

Warnings: low downloads.

Negative: stale.

## Facts

| | |
|---|---|
| Version | 8.5.2 |
| Published | 2025-07-01 |
| First published | 2018-09-14 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Node | >=0.4.0 |
| Dependencies | 1 |
| Unpacked size | 119.4 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 11450 |
| Maintainers | marijn, adrianheine, rreverser |

## Links

- npm: https://www.npmjs.com/package/acorn-loose
- Repository: https://github.com/acornjs/acorn
- Issues: https://github.com/acornjs/acorn/issues
- npm.io page: https://npm.io/package/acorn-loose

## Dependencies (1)

- [acorn](https://npm.io/package/acorn.md) ^8.15.0

## Recent versions

- 8.5.2 (latest) — 2025-07-01
- 8.5.1 — 2025-06-08
- 8.5.0 — 2025-04-17
- 8.4.0 — 2023-10-26
- 8.3.0 — 2021-12-27
- 8.2.1 — 2021-09-06
- 8.2.0 — 2021-09-06
- 8.1.0 — 2021-04-24
- 8.0.2 — 2021-01-25
- 8.0.1 — 2020-10-11
- 8.0.0 — 2020-08-12
- 7.1.0 — 2020-06-11
- 7.0.0 — 2019-08-13
- 6.1.0 — 2019-07-04
- 6.0.0 — 2018-09-14

## README

# Acorn loose parser

An error-tolerant JavaScript parser written in JavaScript.

This parser will parse _any_ text into an
[ESTree](https://github.com/estree/estree) syntax tree that is a
reasonable approximation of what it might mean as a JavaScript
program.

It will, to recover from missing brackets, treat whitespace as
significant, which has the downside that it might mis-parse a valid
but weirdly indented file. It is recommended to always try a parse
with the regular `acorn` parser first, and only fall back to this
parser when that one finds syntax errors.

## Community

Acorn is open source software released under an
[MIT license](https://github.com/acornjs/acorn/blob/master/acorn-loose/LICENSE).

You are welcome to [report
bugs](https://github.com/acornjs/acorn/issues) or create pull requests
on [github](https://github.com/acornjs/acorn).

## Installation

The easiest way to install acorn-loose is from [`npm`](https://www.npmjs.com/):

```sh
npm install acorn-loose
```

Alternately, you can download the source and build acorn yourself:

```sh
git clone https://github.com/acornjs/acorn.git
cd acorn
npm install
```

## Interface

**parse**`(input, options)` takes an input string and a set of options
(the same options as
[acorn](https://github.com/acornjs/acorn/blob/master/acorn/README.md)
takes), and returns a syntax tree, even if the code isn't
syntactically valid. It'll insert identifier nodes with name `"✖"` as
placeholders in places where it can't make sense of the input. Depends
on the `acorn` package, because it uses the same tokenizer.

```javascript
var acornLoose = require("acorn-loose");
console.log(acornLoose.parse("1 / * 4 )[2]", {ecmaVersion: 2020}));
```

Like the regular parser, the loose parser supports plugins. You can
take the **`LooseParser`** class exported by the module, and call its
static `extend` method with one or more plugins to get a customized
parser class. The class has a static `parse` method that acts like the
top-level `parse` method.

**isDummy**`(node)` takes a `Node` and returns `true` if it is a dummy node
inserted by the parser. The function performs a simple equality check on the
node's name.

---
_Source: https://npm.io/package/acorn-loose · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._