https://github.com/not-an-aardvark/js-numeric-literal-parser

Parser for JS numeric literals
https://github.com/not-an-aardvark/js-numeric-literal-parser

Last synced: about 1 month ago
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Parser for JS numeric literals

• Host: GitHub
• URL: https://github.com/not-an-aardvark/js-numeric-literal-parser
• Owner: not-an-aardvark
• License: mit
• Created: 2019-01-17T23:15:46.000Z (almost 6 years ago)
• Default Branch: master
• Last Pushed: 2019-01-17T23:24:47.000Z (almost 6 years ago)
• Last Synced: 2024-11-23T02:05:01.042Z (about 1 month ago)
• Language: JavaScript
• Size: 4.88 KB
• Stars: 0
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE.md

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README

        
# numeric-literal-parser

A parser for JavaScript numeric literals

```bash

$ npm install numeric-literal-parser

```

```js

const parser = require('numeric-literal-parser');

parser.parse('0XdeadBEEF');

/* Output:

   {

     type: 'HexInteger',

     prefix: '0X',

     digits: [ 'd', 'e', 'a', 'd', 'B', 'E', 'E', 'F' ]

   } */

```

## Goals

* Correctness: Parse trees should be correct according to the TC39 spec, including Annex B.

* Full Information: Parse trees should have enough information to reproduce the input string. (This parser is intended for static analysis tools, and it's difficult to determine what aspect of the literal a particular tool might care about, so nothing is omitted.)

## API

This module exports an object with two properties: `parse` and `SyntaxError`. `parse` is a function that accepts a string and returns a parse tree if the parse was successful, or throws an instance of `SyntaxError` if the parse was unsuccessful. 

Parse trees have the following type:

```typescript

type ParseTree =

  {

    type: 'Decimal',

    integralDigits: string[],

    decimalPoint: '.' | null,

    fractionalDigits: string[],

    exponent: {

      exponentIndicator: 'e' | 'E',

      sign: '+' | '-' | null,

      digits: string[]

    } | null

  } |

  {

    type: 'BinaryInteger',

    prefix: '0b' | '0B',

    digits: string[]

  } |

  {

    type: 'OctalInteger',

    prefix: '0o' | '0O',

    digits: string[]

  } |

  {

    type: 'HexInteger',

    prefix: '0x' | '0X',

    digits: string[]

  } |

  {

    type: 'LegacyOctalInteger',

    prefix: '0',

    digits: string[]

  };

```

Literals are parsed for "sloppy mode" JS. To parse a literal for strict mode JS, run the parser and then throw an error manually if

* the parse tree has type `LegacyOctalInteger`, or 

* the parse tree has type `Decimal` and multiple integral digits, the first of which is `'0'`.

## Development

The parser specification in `grammar.pegjs`. Run `npm run build` to generate the JavaScript module.

## License

MIT License