| 
						 | 
						- # Acorn
 - 
 - A tiny, fast JavaScript parser written in JavaScript.
 - 
 - ## Community
 - 
 - Acorn is open source software released under an
 - [MIT license](https://github.com/acornjs/acorn/blob/master/acorn/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 is from [`npm`](https://www.npmjs.com/):
 - 
 - ```sh
 - npm install acorn
 - ```
 - 
 - 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)` is the main interface to the library. The
 - `input` parameter is a string, `options` must be an object setting
 - some of the options listed below. The return value will be an abstract
 - syntax tree object as specified by the [ESTree
 - spec](https://github.com/estree/estree).
 - 
 - ```javascript
 - let acorn = require("acorn");
 - console.log(acorn.parse("1 + 1", {ecmaVersion: 2020}));
 - ```
 - 
 - When encountering a syntax error, the parser will raise a
 - `SyntaxError` object with a meaningful message. The error object will
 - have a `pos` property that indicates the string offset at which the
 - error occurred, and a `loc` object that contains a `{line, column}`
 - object referring to that same position.
 - 
 - Options are provided by in a second argument, which should be an
 - object containing any of these fields (only `ecmaVersion` is
 - required):
 - 
 - - **ecmaVersion**: Indicates the ECMAScript version to parse. Can be a
 -   number, either in year (`2022`) or plain version number (`6`) form,
 -   or `"latest"` (the latest the library supports). This influences
 -   support for strict mode, the set of reserved words, and support for
 -   new syntax features.
 - 
 -   **NOTE**: Only 'stage 4' (finalized) ECMAScript features are being
 -   implemented by Acorn. Other proposed new features must be
 -   implemented through plugins.
 - 
 - - **sourceType**: Indicate the mode the code should be parsed in. Can be
 -   either `"script"` or `"module"`. This influences global strict mode
 -   and parsing of `import` and `export` declarations.
 - 
 -   **NOTE**: If set to `"module"`, then static `import` / `export` syntax
 -   will be valid, even if `ecmaVersion` is less than 6.
 - 
 - - **onInsertedSemicolon**: If given a callback, that callback will be
 -   called whenever a missing semicolon is inserted by the parser. The
 -   callback will be given the character offset of the point where the
 -   semicolon is inserted as argument, and if `locations` is on, also a
 -   `{line, column}` object representing this position.
 - 
 - - **onTrailingComma**: Like `onInsertedSemicolon`, but for trailing
 -   commas.
 - 
 - - **allowReserved**: If `false`, using a reserved word will generate
 -   an error. Defaults to `true` for `ecmaVersion` 3, `false` for higher
 -   versions. When given the value `"never"`, reserved words and
 -   keywords can also not be used as property names (as in Internet
 -   Explorer's old parser).
 - 
 - - **allowReturnOutsideFunction**: By default, a return statement at
 -   the top level raises an error. Set this to `true` to accept such
 -   code.
 - 
 - - **allowImportExportEverywhere**: By default, `import` and `export`
 -   declarations can only appear at a program's top level. Setting this
 -   option to `true` allows them anywhere where a statement is allowed,
 -   and also allows `import.meta` expressions to appear in scripts
 -   (when `sourceType` is not `"module"`).
 - 
 - - **allowAwaitOutsideFunction**: If `false`, `await` expressions can
 -   only appear inside `async` functions. Defaults to `true` in modules
 -   for `ecmaVersion` 2022 and later, `false` for lower versions.
 -   Setting this option to `true` allows to have top-level `await`
 -   expressions. They are still not allowed in non-`async` functions,
 -   though.
 - 
 - - **allowSuperOutsideMethod**: By default, `super` outside a method
 -   raises an error. Set this to `true` to accept such code.
 - 
 - - **allowHashBang**: When this is enabled, if the code starts with the
 -   characters `#!` (as in a shellscript), the first line will be
 -   treated as a comment. Defaults to true when `ecmaVersion` >= 2023.
 - 
 - - **checkPrivateFields**: By default, the parser will verify that
 -   private properties are only used in places where they are valid and
 -   have been declared. Set this to false to turn such checks off.
 - 
 - - **locations**: When `true`, each node has a `loc` object attached
 -   with `start` and `end` subobjects, each of which contains the
 -   one-based line and zero-based column numbers in `{line, column}`
 -   form. Default is `false`.
 - 
 - - **onToken**: If a function is passed for this option, each found
 -   token will be passed in same format as tokens returned from
 -   `tokenizer().getToken()`.
 - 
 -   If array is passed, each found token is pushed to it.
 - 
 -   Note that you are not allowed to call the parser from the
 -   callback—that will corrupt its internal state.
 - 
 - - **onComment**: If a function is passed for this option, whenever a
 -   comment is encountered the function will be called with the
 -   following parameters:
 - 
 -   - `block`: `true` if the comment is a block comment, false if it
 -     is a line comment.
 -   - `text`: The content of the comment.
 -   - `start`: Character offset of the start of the comment.
 -   - `end`: Character offset of the end of the comment.
 - 
 -   When the `locations` options is on, the `{line, column}` locations
 -   of the comment’s start and end are passed as two additional
 -   parameters.
 - 
 -   If array is passed for this option, each found comment is pushed
 -   to it as object in Esprima format:
 - 
 -   ```javascript
 -   {
 -     "type": "Line" | "Block",
 -     "value": "comment text",
 -     "start": Number,
 -     "end": Number,
 -     // If `locations` option is on:
 -     "loc": {
 -       "start": {line: Number, column: Number}
 -       "end": {line: Number, column: Number}
 -     },
 -     // If `ranges` option is on:
 -     "range": [Number, Number]
 -   }
 -   ```
 - 
 -   Note that you are not allowed to call the parser from the
 -   callback—that will corrupt its internal state.
 - 
 - - **ranges**: Nodes have their start and end characters offsets
 -   recorded in `start` and `end` properties (directly on the node,
 -   rather than the `loc` object, which holds line/column data. To also
 -   add a
 -   [semi-standardized](https://bugzilla.mozilla.org/show_bug.cgi?id=745678)
 -   `range` property holding a `[start, end]` array with the same
 -   numbers, set the `ranges` option to `true`.
 - 
 - - **program**: It is possible to parse multiple files into a single
 -   AST by passing the tree produced by parsing the first file as the
 -   `program` option in subsequent parses. This will add the toplevel
 -   forms of the parsed file to the "Program" (top) node of an existing
 -   parse tree.
 - 
 - - **sourceFile**: When the `locations` option is `true`, you can pass
 -   this option to add a `source` attribute in every node’s `loc`
 -   object. Note that the contents of this option are not examined or
 -   processed in any way; you are free to use whatever format you
 -   choose.
 - 
 - - **directSourceFile**: Like `sourceFile`, but a `sourceFile` property
 -   will be added (regardless of the `location` option) directly to the
 -   nodes, rather than the `loc` object.
 - 
 - - **preserveParens**: If this option is `true`, parenthesized expressions
 -   are represented by (non-standard) `ParenthesizedExpression` nodes
 -   that have a single `expression` property containing the expression
 -   inside parentheses.
 - 
 - **parseExpressionAt**`(input, offset, options)` will parse a single
 - expression in a string, and return its AST. It will not complain if
 - there is more of the string left after the expression.
 - 
 - **tokenizer**`(input, options)` returns an object with a `getToken`
 - method that can be called repeatedly to get the next token, a `{start,
 - end, type, value}` object (with added `loc` property when the
 - `locations` option is enabled and `range` property when the `ranges`
 - option is enabled). When the token's type is `tokTypes.eof`, you
 - should stop calling the method, since it will keep returning that same
 - token forever.
 - 
 - Note that tokenizing JavaScript without parsing it is, in modern
 - versions of the language, not really possible due to the way syntax is
 - overloaded in ways that can only be disambiguated by the parse
 - context. This package applies a bunch of heuristics to try and do a
 - reasonable job, but you are advised to use `parse` with the `onToken`
 - option instead of this.
 - 
 - In ES6 environment, returned result can be used as any other
 - protocol-compliant iterable:
 - 
 - ```javascript
 - for (let token of acorn.tokenizer(str)) {
 -   // iterate over the tokens
 - }
 - 
 - // transform code to array of tokens:
 - var tokens = [...acorn.tokenizer(str)];
 - ```
 - 
 - **tokTypes** holds an object mapping names to the token type objects
 - that end up in the `type` properties of tokens.
 - 
 - **getLineInfo**`(input, offset)` can be used to get a `{line,
 - column}` object for a given program string and offset.
 - 
 - ### The `Parser` class
 - 
 - Instances of the **`Parser`** class contain all the state and logic
 - that drives a parse. It has static methods `parse`,
 - `parseExpressionAt`, and `tokenizer` that match the top-level
 - functions by the same name.
 - 
 - When extending the parser with plugins, you need to call these methods
 - on the extended version of the class. To extend a parser with plugins,
 - you can use its static `extend` method.
 - 
 - ```javascript
 - var acorn = require("acorn");
 - var jsx = require("acorn-jsx");
 - var JSXParser = acorn.Parser.extend(jsx());
 - JSXParser.parse("foo(<bar/>)", {ecmaVersion: 2020});
 - ```
 - 
 - The `extend` method takes any number of plugin values, and returns a
 - new `Parser` class that includes the extra parser logic provided by
 - the plugins.
 - 
 - ## Command line interface
 - 
 - The `bin/acorn` utility can be used to parse a file from the command
 - line. It accepts as arguments its input file and the following
 - options:
 - 
 - - `--ecma3|--ecma5|--ecma6|--ecma7|--ecma8|--ecma9|--ecma10`: Sets the ECMAScript version
 -   to parse. Default is version 9.
 - 
 - - `--module`: Sets the parsing mode to `"module"`. Is set to `"script"` otherwise.
 - 
 - - `--locations`: Attaches a "loc" object to each node with "start" and
 -   "end" subobjects, each of which contains the one-based line and
 -   zero-based column numbers in `{line, column}` form.
 - 
 - - `--allow-hash-bang`: If the code starts with the characters #! (as
 -   in a shellscript), the first line will be treated as a comment.
 - 
 - - `--allow-await-outside-function`: Allows top-level `await` expressions.
 -   See the `allowAwaitOutsideFunction` option for more information.
 - 
 - - `--compact`: No whitespace is used in the AST output.
 - 
 - - `--silent`: Do not output the AST, just return the exit status.
 - 
 - - `--help`: Print the usage information and quit.
 - 
 - The utility spits out the syntax tree as JSON data.
 - 
 - ## Existing plugins
 - 
 -  - [`acorn-jsx`](https://github.com/RReverser/acorn-jsx): Parse [Facebook JSX syntax extensions](https://github.com/facebook/jsx)
 
 
  |