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Snapdragon util and plugin for patching the position on an AST node.

Please consider following this project's author, Jon Schlinkert, and consider starring the project to show your :heart: and support.

Install

Install with npm:

$ npm install --save snapdragon-position

What does this do?

Adds a .position object to tokens that looks something like this:

{
  source: 'string',
  start: { index: 0, column: 1, line: 1 },
  end: { index: 3, column: 4, line: 1 },
  range: [0, 3] // getter
}

When used as snapdragon-lexer plugin, this adds a .position() method to the instance and patches the lexer.lex() and lexer.handle() methods to automatically add position objects to tokens.

There is a more detailed example below.

Heads up!

If you would prefer for the property name to be token.loc rather than token.position, use snapdragon-location instead.

API

The main export is a function that can be used as a plugin with snapdragon-lexer, or called directly with an instance of snapdragon-lexer.

position

Sets the start position and returns a function for setting the end position on a token.

Params

Example

const position = require('snapdragon-position');
const Lexer = require('snapdragon-lexer');
const lexer = new Lexer('foo/bar');

lexer.capture('slash', /^\//);
lexer.capture('text', /^\w+/);

const pos = position(lexer);
const token = pos(lexer.advance());
console.log(token);

.plugin

Use as a plugin to add a .position method to your snapdragon-lexer or [snapdragon-tokenizer][] instance to automatically add a position object to tokens when the .lex() or .handle() methods are used.

Example

const Lexer = require('snapdragon-lexer');
const position = require('snapdragon-position');
const lexer = new Lexer();
lexer.use(position());

.location

Get the current source location, with index, column and line. Used by .position() to create the "start" and "end" locations.

Example

const Lexer = require('snapdragon-lexer');
const lexer = new Lexer();
console.log(lexer.location());
//=> Location { index: 0, column: 0, line: 1 };

.position

Returns a function for getting the current position.

Example

const Lexer = require('snapdragon-lexer');
const lexer = new Lexer('foo/bar');
lexer.use(position());

lexer.set('text', function(tok) {
  // get start position before advancing lexer
  const pos = this.position();
  const match = this.match(/^\w+/);
  if (match) {
    // get end position after advancing lexer (with .match)
    return pos(this.token(match));
  }
});

Params

Example

const Lexer = require('snapdragon-lexer');
const Location = require('snapdragon-position').Location;
const lexer = new Lexer('foo/bar');
lexer.capture('text', /^\w+/);
lexer.advance();
console.log(new Location(lexer));
//=> Location { index: 3, column: 4, line: 1 }

Params

Example

const Lexer = require('snapdragon-lexer');
const position = require('snapdragon-location');
const lexer = new Lexer('foo/bar')
  .capture('slash', /^\//)
  .capture('text', /^\w+/);

const start = new position.Location(lexer);
lexer.advance();
const end = new position.Location(lexer);
console.log(new position.Position(start, end, lexer));
// Position {
//   source: undefined,
//   start: Location { index: 0, column: 1, line: 1 },
//   end: Location { index: 3, column: 4, line: 1 } }

Plugin usage

When used as a plugin, this adds a .position() method to a snapdragon-lexer instance, for adding position information to tokens.

Example

const position = require('snapdragon-position');
const Lexer = require('snapdragon-lexer');
const lexer = new Lexer('foo/bar');
lexer.use(position());

lexer.capture('slash', /^\//);
lexer.capture('text', /^\w+/);

var token = lexer.advance();
console.log(token);

Adds a .position object to the token, like this:

Token {
  type: 'text',
  value: 'foo',
  match: [ 'foo', index: 0, input: 'foo/*' ],
  position: {
    start: { index: 0, column: 1, line: 1 },
    end: { index: 3, column: 4, line: 1 },
    range: [0, 3] // getter
  } 
}

Token objects

See the Token documentation for more details about the Token object.

interface Token {
  type: string;
  value: string;
  match: array | undefined;
  position: Position;
}

Position objects

The token.position property contains source string position information on the token.

interface Position {
  source: string | undefined;
  start: Location;
  end: Location;
  range: array (getter)
}

Location objects

Each Location object consists of an index number (0-based), a column number (0-based), and a line number (1-based):

interface Location {
  index: number; // >= 0
  column: number; // >= 0,
  line: number; // >= 1
}

Example usage

const Lexer = require('snapdragon-lexer');
const lexer = new Lexer('foo/*', { source: 'string' });
lexer.use(position());
lexer.capture('star', /^\*/);
lexer.capture('slash', /^\//);
lexer.capture('text', /^\w+/);

lexer.tokenize();
console.log(lexer.tokens);

Results in:

[
  {
    type: 'text',
    val: 'foo',
    match: ['foo', index: 0, input: 'foo/*'],
    position: {
      source: 'string',
      start: { index: 0, column: 1, line: 1 },
      end: { index: 3, column: 4, line: 1 },
      range: [0, 3]
    }
  },
  {
    type: 'slash',
    val: '/',
    match: ['/', index: 0, input: '/*'],
    position: {
      source: 'string',
      start: { index: 3, column: 4, line: 1 },
      end: { index: 4, column: 5, line: 1 },
      range: [3, 4]
    }
  },
  {
    type: 'star',
    val: '*',
    match: ['*', index: 0, input: '*'],
    position: {
      source: 'string',
      start: { index: 4, column: 5, line: 1 },
      end: { index: 5, column: 6, line: 1 },
      range: [4, 5]
    }
  }
]

About

<details> <summary><strong>Contributing</strong></summary>

Pull requests and stars are always welcome. For bugs and feature requests, please create an issue.

Please read the contributing guide for advice on opening issues, pull requests, and coding standards.

</details> <details> <summary><strong>Running Tests</strong></summary>

Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:

$ npm install && npm test
</details> <details> <summary><strong>Building docs</strong></summary>

(This project's readme.md is generated by verb, please don't edit the readme directly. Any changes to the readme must be made in the .verb.md readme template.)

To generate the readme, run the following command:

$ npm install -g verbose/verb#dev verb-generate-readme && verb
</details>

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Author

Jon Schlinkert

License

Copyright © 2018, Jon Schlinkert. Released under the MIT License.


This file was generated by verb-generate-readme, v0.6.0, on January 08, 2018.