--- /dev/null
+# 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). For questions
+and discussion, please use the
+[Tern discussion forum](https://discuss.ternjs.net).
+
+## 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` can be undefined or 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"));
+```
+
+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 can be provided by passing a second argument, which should be
+an object containing any of these fields:
+
+- **ecmaVersion**: Indicates the ECMAScript version to parse. Must be
+ either 3, 5, 6 (2015), 7 (2016), 8 (2017), 9 (2018), 10 (2019) or 11
+ (2020, partial support). This influences support for strict mode,
+ the set of reserved words, and support for new syntax features.
+ Default is 10.
+
+ **NOTE**: Only 'stage 4' (finalized) ECMAScript features are being
+ implemented by Acorn. Other proposed new features can 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.
+
+- **allowAwaitOutsideFunction**: By default, `await` expressions can
+ only appear inside `async` functions. Setting this option to
+ `true` allows to have top-level `await` expressions. They are
+ still not allowed in non-`async` functions, though.
+
+- **allowHashBang**: When this is enabled (off by default), if the
+ code starts with the characters `#!` (as in a shellscript), the
+ first line will be treated as a comment.
+
+- **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.
+
+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/>)");
+```
+
+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.
+
+- `--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)
+
+Plugins for ECMAScript proposals:
+
+ - [`acorn-stage3`](https://github.com/acornjs/acorn-stage3): Parse most stage 3 proposals, bundling:
+ - [`acorn-class-fields`](https://github.com/acornjs/acorn-class-fields): Parse [class fields proposal](https://github.com/tc39/proposal-class-fields)
+ - [`acorn-import-meta`](https://github.com/acornjs/acorn-import-meta): Parse [import.meta proposal](https://github.com/tc39/proposal-import-meta)
+ - [`acorn-numeric-separator`](https://github.com/acornjs/acorn-numeric-separator): Parse [numeric separator proposal](https://github.com/tc39/proposal-numeric-separator)
+ - [`acorn-private-methods`](https://github.com/acornjs/acorn-private-methods): parse [private methods, getters and setters proposal](https://github.com/tc39/proposal-private-methods)n
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