snapdragon-util

What is snapdragon-util?

The snapdragon-util npm package provides utility functions for working with AST (Abstract Syntax Tree) nodes, which are commonly used in parsers and compilers. It offers a set of tools to manipulate, visit, and manage AST nodes effectively.

What are snapdragon-util's main functionalities?

Visit Nodes

This feature allows you to visit each node in an AST. The provided code sample demonstrates how to traverse an AST and log the type of each node.

const util = require('snapdragon-util');
const ast = { type: 'root', nodes: [{ type: 'text', value: 'Hello' }, { type: 'text', value: 'World' }] };
util.visit(ast, node => console.log(node.type));

Map Nodes

This feature allows you to map over each node in an AST and transform it. The provided code sample demonstrates how to convert the text values of nodes to uppercase.

const util = require('snapdragon-util');
const ast = { type: 'root', nodes: [{ type: 'text', value: 'Hello' }, { type: 'text', value: 'World' }] };
const newAst = util.map(ast, node => {
  if (node.type === 'text') {
    node.value = node.value.toUpperCase();
  }
  return node;
});
console.log(newAst);

Filter Nodes

This feature allows you to filter nodes in an AST based on a condition. The provided code sample demonstrates how to filter nodes that have a value of 'Hello'.

const util = require('snapdragon-util');
const ast = { type: 'root', nodes: [{ type: 'text', value: 'Hello' }, { type: 'text', value: 'World' }] };
const filteredNodes = util.filter(ast, node => node.value === 'Hello');
console.log(filteredNodes);

Other packages similar to snapdragon-util

estraverse

Estraverse is a tool for ECMAScript/JavaScript to traverse and manipulate the syntax tree. It provides similar functionalities to snapdragon-util, such as visiting and modifying nodes in an AST.

esquery

Esquery is a library for querying JavaScript ASTs with a CSS-like selector syntax. It offers a different approach to manipulating ASTs compared to snapdragon-util, focusing on querying and selecting nodes.

babel-traverse

Babel-traverse maintains the overall tree structure and provides a simple way to perform operations on nodes. It is part of the Babel toolchain and offers extensive functionality for AST manipulation, similar to snapdragon-util.

README

snapdragon-util

Utilities for the snapdragon parser/compiler.

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-util

Usage

var util = require('snapdragon-util');

API

.isNode

Returns true if the given value is a node.

Params

• node {Object}: Instance of snapdragon-node
• returns {Boolean}

Example

var Node = require('snapdragon-node');
var node = new Node({type: 'foo'});
console.log(utils.isNode(node)); //=> true
console.log(utils.isNode({})); //=> false

.noop

Emit an empty string for the given node.

Params

• node {Object}: Instance of snapdragon-node
• returns {undefined}

Example

// do nothing for beginning-of-string
snapdragon.compiler.set('bos', utils.noop);

.value

Returns node.value or node.val.

Params

• node {Object}: Instance of snapdragon-node
• returns {String}: returns

Example

const star = new Node({type: 'star', value: '*'});
const slash = new Node({type: 'slash', val: '/'});
console.log(utils.value(star)) //=> '*'
console.log(utils.value(slash)) //=> '/'

.identity

Append node.value to compiler.output.

Params

• node {Object}: Instance of snapdragon-node
• returns {undefined}

Example

snapdragon.compiler.set('text', utils.identity);

.append

Previously named .emit, this method appends the given value to compiler.output for the given node. Useful when you know what value should be appended advance, regardless of the actual value of node.value.

Params

• node {Object}: Instance of snapdragon-node
• returns {Function}: Returns a compiler middleware function.

Example

snapdragon.compiler
  .set('i', function(node) {
    this.mapVisit(node);
  })
  .set('i.open', utils.append('<i>'))
  .set('i.close', utils.append('</i>'))

.toNoop

Used in compiler middleware, this onverts an AST node into an empty text node and deletes node.nodes if it exists. The advantage of this method is that, as opposed to completely removing the node, indices will not need to be re-calculated in sibling nodes, and nothing is appended to the output.

Params

• node {Object}: Instance of snapdragon-node
• nodes {Array}: Optionally pass a new nodes value, to replace the existing node.nodes array.

Example

utils.toNoop(node);
// convert `node.nodes` to the given value instead of deleting it
utils.toNoop(node, []);

.visit

Visit node with the given fn. The built-in .visit method in snapdragon automatically calls registered compilers, this allows you to pass a visitor function.

Params

• node {Object}: Instance of snapdragon-node
• fn {Function}
• returns {Object}: returns the node after recursively visiting all child nodes.

Example

snapdragon.compiler.set('i', function(node) {
  utils.visit(node, function(childNode) {
    // do stuff with "childNode"
    return childNode;
  });
});

.mapVisit

Map visit the given fn over node.nodes. This is called by visit, use this method if you do not want fn to be called on the first node.

Params

• node {Object}: Instance of snapdragon-node
• options {Object}
• fn {Function}
• returns {Object}: returns the node

Example

snapdragon.compiler.set('i', function(node) {
  utils.mapVisit(node, function(childNode) {
    // do stuff with "childNode"
    return childNode;
  });
});

.addOpen

Unshift an *.open node onto node.nodes.

Params

• node {Object}: Instance of snapdragon-node
• Node {Function}: (required) Node constructor function from snapdragon-node.
• filter {Function}: Optionaly specify a filter function to exclude the node.
• returns {Object}: Returns the created opening node.

Example

var Node = require('snapdragon-node');
snapdragon.parser.set('brace', function(node) {
  var match = this.match(/^{/);
  if (match) {
    var parent = new Node({type: 'brace'});
    utils.addOpen(parent, Node);
    console.log(parent.nodes[0]):
    // { type: 'brace.open', value: '' };

    // push the parent "brace" node onto the stack
    this.push(parent);

    // return the parent node, so it's also added to the AST
    return brace;
  }
});

.addClose

Push a *.close node onto node.nodes.

Params

• node {Object}: Instance of snapdragon-node
• Node {Function}: (required) Node constructor function from snapdragon-node.
• filter {Function}: Optionaly specify a filter function to exclude the node.
• returns {Object}: Returns the created closing node.

Example

var Node = require('snapdragon-node');
snapdragon.parser.set('brace', function(node) {
  var match = this.match(/^}/);
  if (match) {
    var parent = this.parent();
    if (parent.type !== 'brace') {
      throw new Error('missing opening: ' + '}');
    }

    utils.addClose(parent, Node);
    console.log(parent.nodes[parent.nodes.length - 1]):
    // { type: 'brace.close', value: '' };

    // no need to return a node, since the parent
    // was already added to the AST
    return;
  }
});

.wrapNodes

Wraps the given node with *.open and *.close nodes.

Params

• node {Object}: Instance of snapdragon-node
• Node {Function}: (required) Node constructor function from snapdragon-node.
• filter {Function}: Optionaly specify a filter function to exclude the node.
• returns {Object}: Returns the node

.pushNode

Push the given node onto parent.nodes, and set parent as `node.parent.

Params

• parent {Object}
• node {Object}: Instance of snapdragon-node
• returns {Object}: Returns the child node

Example

var parent = new Node({type: 'foo'});
var node = new Node({type: 'bar'});
utils.pushNode(parent, node);
console.log(parent.nodes[0].type) // 'bar'
console.log(node.parent.type) // 'foo'

.unshiftNode

Unshift node onto parent.nodes, and set parent as `node.parent.

Params

• parent {Object}
• node {Object}: Instance of snapdragon-node
• returns {undefined}

Example

var parent = new Node({type: 'foo'});
var node = new Node({type: 'bar'});
utils.unshiftNode(parent, node);
console.log(parent.nodes[0].type) // 'bar'
console.log(node.parent.type) // 'foo'

.popNode

Pop the last node off of parent.nodes. The advantage of using this method is that it checks for node.nodes and works with any version of snapdragon-node.

Params

• parent {Object}
• node {Object}: Instance of snapdragon-node
• returns {Number|Undefined}: Returns the length of node.nodes or undefined.

Example

var parent = new Node({type: 'foo'});
utils.pushNode(parent, new Node({type: 'foo'}));
utils.pushNode(parent, new Node({type: 'bar'}));
utils.pushNode(parent, new Node({type: 'baz'}));
console.log(parent.nodes.length); //=> 3
utils.popNode(parent);
console.log(parent.nodes.length); //=> 2

.shiftNode

Shift the first node off of parent.nodes. The advantage of using this method is that it checks for node.nodes and works with any version of snapdragon-node.

Params

• parent {Object}
• node {Object}: Instance of snapdragon-node
• returns {Number|Undefined}: Returns the length of node.nodes or undefined.

Example

var parent = new Node({type: 'foo'});
utils.pushNode(parent, new Node({type: 'foo'}));
utils.pushNode(parent, new Node({type: 'bar'}));
utils.pushNode(parent, new Node({type: 'baz'}));
console.log(parent.nodes.length); //=> 3
utils.shiftNode(parent);
console.log(parent.nodes.length); //=> 2

.removeNode

Remove the specified node from parent.nodes.

Params

• parent {Object}
• node {Object}: Instance of snapdragon-node
• returns {Object|undefined}: Returns the removed node, if successful, or undefined if it does not exist on parent.nodes.

Example

var parent = new Node({type: 'abc'});
var foo = new Node({type: 'foo'});
utils.pushNode(parent, foo);
utils.pushNode(parent, new Node({type: 'bar'}));
utils.pushNode(parent, new Node({type: 'baz'}));
console.log(parent.nodes.length); //=> 3
utils.removeNode(parent, foo);
console.log(parent.nodes.length); //=> 2

.isType

Returns true if node.type matches the given type. Throws a TypeError if node is not an instance of Node.

Params

• node {Object}: Instance of snapdragon-node
• type {String}
• returns {Boolean}

Example

var Node = require('snapdragon-node');
var node = new Node({type: 'foo'});
console.log(utils.isType(node, 'foo')); // false
console.log(utils.isType(node, 'bar')); // true

.hasType

Returns true if the given node has the given type in node.nodes. Throws a TypeError if node is not an instance of Node.

Params

• node {Object}: Instance of snapdragon-node
• type {String}
• returns {Boolean}

Example

var Node = require('snapdragon-node');
var node = new Node({
  type: 'foo',
  nodes: [
    new Node({type: 'bar'}),
    new Node({type: 'baz'})
  ]
});
console.log(utils.hasType(node, 'xyz')); // false
console.log(utils.hasType(node, 'baz')); // true

.firstOfType

Returns the first node from node.nodes of the given type

Params

• nodes {Array}
• type {String}
• returns {Object|undefined}: Returns the first matching node or undefined.

Example

var node = new Node({
  type: 'foo',
  nodes: [
    new Node({type: 'text', value: 'abc'}),
    new Node({type: 'text', value: 'xyz'})
  ]
});

var textNode = utils.firstOfType(node.nodes, 'text');
console.log(textNode.value);
//=> 'abc'

.findNode

Returns the node at the specified index, or the first node of the given type from node.nodes.

Params

• nodes {Array}
• type {String|Number}: Node type or index.
• returns {Object}: Returns a node or undefined.

Example

var node = new Node({
  type: 'foo',
  nodes: [
    new Node({type: 'text', value: 'abc'}),
    new Node({type: 'text', value: 'xyz'})
  ]
});

var nodeOne = utils.findNode(node.nodes, 'text');
console.log(nodeOne.value);
//=> 'abc'

var nodeTwo = utils.findNode(node.nodes, 1);
console.log(nodeTwo.value);
//=> 'xyz'

.isOpen

Returns true if the given node is an "*.open" node.

Params

• node {Object}: Instance of snapdragon-node
• returns {Boolean}

Example

var Node = require('snapdragon-node');
var brace = new Node({type: 'brace'});
var open = new Node({type: 'brace.open'});
var close = new Node({type: 'brace.close'});

console.log(utils.isOpen(brace)); // false
console.log(utils.isOpen(open)); // true
console.log(utils.isOpen(close)); // false

.isClose

Returns true if the given node is a "*.close" node.

Params

• node {Object}: Instance of snapdragon-node
• returns {Boolean}

Example

var Node = require('snapdragon-node');
var brace = new Node({type: 'brace'});
var open = new Node({type: 'brace.open'});
var close = new Node({type: 'brace.close'});

console.log(utils.isClose(brace)); // false
console.log(utils.isClose(open)); // false
console.log(utils.isClose(close)); // true

.isBlock

Returns true if the given node is an "*.open" node.

Params

• node {Object}: Instance of snapdragon-node
• returns {Boolean}

Example

var Node = require('snapdragon-node');
var brace = new Node({type: 'brace'});
var open = new Node({type: 'brace.open', value: '{'});
var inner = new Node({type: 'text', value: 'a,b,c'});
var close = new Node({type: 'brace.close', value: '}'});
brace.push(open);
brace.push(inner);
brace.push(close);

console.log(utils.isBlock(brace)); // true

.hasNode

Returns true if parent.nodes has the given node.

Params

• type {String}
• returns {Boolean}

Example

const foo = new Node({type: 'foo'});
const bar = new Node({type: 'bar'});
cosole.log(util.hasNode(foo, bar)); // false
foo.push(bar);
cosole.log(util.hasNode(foo, bar)); // true

.hasOpen

Returns true if node.nodes has an .open node

Params

• node {Object}: Instance of snapdragon-node
• returns {Boolean}

Example

var Node = require('snapdragon-node');
var brace = new Node({
  type: 'brace',
  nodes: []
});

var open = new Node({type: 'brace.open'});
console.log(utils.hasOpen(brace)); // false

brace.pushNode(open);
console.log(utils.hasOpen(brace)); // true

.hasClose

Returns true if node.nodes has a .close node

Params

• node {Object}: Instance of snapdragon-node
• returns {Boolean}

Example

var Node = require('snapdragon-node');
var brace = new Node({
  type: 'brace',
  nodes: []
});

var close = new Node({type: 'brace.close'});
console.log(utils.hasClose(brace)); // false

brace.pushNode(close);
console.log(utils.hasClose(brace)); // true

.hasOpenAndClose

Returns true if node.nodes has both .open and .close nodes

Params

• node {Object}: Instance of snapdragon-node
• returns {Boolean}

Example

var Node = require('snapdragon-node');
var brace = new Node({
  type: 'brace',
  nodes: []
});

var open = new Node({type: 'brace.open'});
var close = new Node({type: 'brace.close'});
console.log(utils.hasOpen(brace)); // false
console.log(utils.hasClose(brace)); // false

brace.pushNode(open);
brace.pushNode(close);
console.log(utils.hasOpen(brace)); // true
console.log(utils.hasClose(brace)); // true

.addType

Push the given node onto the state.inside array for the given type. This array is used as a specialized "stack" for only the given node.type.

Params

• state {Object}: The compiler.state object or custom state object.
• node {Object}: Instance of snapdragon-node
• returns {Array}: Returns the state.inside stack for the given type.

Example

var state = { inside: {}};
var node = new Node({type: 'brace'});
utils.addType(state, node);
console.log(state.inside);
//=> { brace: [{type: 'brace'}] }

.removeType

Remove the given node from the state.inside array for the given type. This array is used as a specialized "stack" for only the given node.type.

Params

• state {Object}: The compiler.state object or custom state object.
• node {Object}: Instance of snapdragon-node
• returns {Array}: Returns the state.inside stack for the given type.

Example

var state = { inside: {}};
var node = new Node({type: 'brace'});
utils.addType(state, node);
console.log(state.inside);
//=> { brace: [{type: 'brace'}] }
utils.removeType(state, node);
//=> { brace: [] }

.isEmpty

Returns true if node.value is an empty string, or node.nodes does not contain any non-empty text nodes.

Params

• node {Object}: Instance of snapdragon-node
• fn {Function}
• returns {Boolean}

Example

var node = new Node({type: 'text'});
utils.isEmpty(node); //=> true
node.value = 'foo';
utils.isEmpty(node); //=> false

.isInsideType

Returns true if the state.inside stack for the given type exists and has one or more nodes on it.

Params

• state {Object}
• type {String}
• returns {Boolean}

Example

var state = { inside: {}};
var node = new Node({type: 'brace'});
console.log(utils.isInsideType(state, 'brace')); //=> false
utils.addType(state, node);
console.log(utils.isInsideType(state, 'brace')); //=> true
utils.removeType(state, node);
console.log(utils.isInsideType(state, 'brace')); //=> false

.isInside

Returns true if node is either a child or grand-child of the given type, or state.inside[type] is a non-empty array.

Params

• state {Object}: Either the compiler.state object, if it exists, or a user-supplied state object.
• node {Object}: Instance of snapdragon-node
• type {String}: The node.type to check for.
• returns {Boolean}

Example

var state = { inside: {}};
var node = new Node({type: 'brace'});
var open = new Node({type: 'brace.open'});
console.log(utils.isInside(state, open, 'brace')); //=> false
utils.pushNode(node, open);
console.log(utils.isInside(state, open, 'brace')); //=> true

.last

Get the last n element from the given array. Used for getting a node from node.nodes.

Params

• array {Array}
• n {Number}
• returns {undefined}

.arrayify

Cast the given value to an array.

Params

• value {any}
• returns {Array}

Example

console.log(utils.arrayify(''));
//=> []
console.log(utils.arrayify('foo'));
//=> ['foo']
console.log(utils.arrayify(['foo']));
//=> ['foo']

.stringify

Convert the given value to a string by joining with ,. Useful for creating a cheerio/CSS/DOM-style selector from a list of strings.

Params

• value {any}
• returns {Array}

.trim

Ensure that the given value is a string and call .trim() on it, or return an empty string.

Params

• str {String}
• returns {String}

About

Contributing

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.

Running Tests

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

Building docs

(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

Related projects

You might also be interested in these projects:

• snapdragon-node: Snapdragon utility for creating a new AST node in custom code, such as plugins. | homepage
• snapdragon-position: Snapdragon util and plugin for patching the position on an AST node. | homepage
• snapdragon-token: Create a snapdragon token. Used by the snapdragon lexer, but can also be used by… more | homepage

Contributors

Commits	Contributor
43	jonschlinkert
2	realityking

Author

Jon Schlinkert

• linkedin/in/jonschlinkert
• github/jonschlinkert
• twitter/jonschlinkert

License

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

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This file was generated by verb-generate-readme, v0.6.0, on January 11, 2018.