QueryAST

[![Build Status][travis-image]][travis-url]
[![NPM version][npm-image]][npm-url]

A library to traverse/modify an AST

Documentation

Read the API documentation

Usage

``javascript
let createQueryWrapper = require('query-ast')
let $ = createQueryWrapper(ast, options)
`

Getting Started

QueryAST aims to provide a jQuery like API for traversing an AST.

`javascript
let ast = {
type: 'program',
value: [{
type: 'item_container',
value: [{
type: 'item',
value: 'a'
}]
}, {
type: 'item_container',
value: []
}, {
type: 'item',
value: 'b'
}]
}

// Create a QueryWrapper that will be used to traverse/modify an AST
let $ = createQueryWrapper(ast)

// By default, the QueryWrapper is scoped to the root node
$('item').length() // 2

// The QueryWrapper can also be scoped to a NodeWrapper or array of NodeWrappers
$('item_container').filter((n) => {
return $(n).has('item')
}).length() // 1
`

$3

Most of the traversal functions take an optional QueryWrapper~Selector argument that will
be use to filter the results.

A selector can be 1 of 3 types:
- string that is compared against the return value of options.getType()
- regexp that is compared against the return value of options.getType()
- function that will be passed a NodeWrapper and expected to return a boolean

`javascript
let ast = {
type: 'program',
value: [{
type: 'item_container',
value: [{
type: 'item',
value: 'a'
}]
}, {
type: 'item',
value: 'b'
}]
}

let $ = createQueryWrapper(ast)

// String
$('item').length() // 2

// RegExp
$(/item/).length() // 3

// Function
$((n) => n.node.value === 'a').length() // 1
`

$3

By default, QueryAST assumes that an AST will be formatted as a node tree
where each node has a type key and a value key that either contains the
string value of the node or an array of child nodes.

`javascript
let ast = {
type: 'program',
value: [{
type: 'item',
value: 'a'
}]
}
`

Alternate formats

Not every AST follows the same format, so QueryAST also provides a way
to traverse any tree structure. Below are the default options used to
handle the above AST structure.

`javascript
let options = {
/**
* Return true if the node has children
*
* @param {object} node
* @returns {boolean}
*/
hasChildren: (node) => Array.isArray(node.value),
/**
* Return an array of child nodes
*
* @param {object} node
* @returns {object[]}
*/
getChildren: (node) => node.value,
/**
* Return a string representation of the node's type
*
* @param {object} node
* @returns {string}
*/
getType: (node) => node.type,
/**
* Convert the node back to JSON. This usually just means merging the
* children back into the node
*
* @param {object} node
* @param {object[]} [children]
* @returns {string}
*/
toJSON: (node, children) => {
return Object.assign({}, node, {
value: children ? children : node.value
})
},
/**
* Convert the node to a string
*
* @param {object} node
* @returns {string}
*/
toString: (node) => {
return typeof node.value === 'string' ? node.value : ''
}
}
`

Running tests

Clone the repository, then:

`bash
npm install


requires node >= 6.0.0


npm test
`

Generate Documentation

`bash
npm run doc
``

[npm-url]: https://npmjs.org/package/query-ast
[npm-image]: http://img.shields.io/npm/v/query-ast.svg

[travis-url]: https://travis-ci.org/salesforce-ux/query-ast
[travis-image]: https://travis-ci.org/salesforce-ux/query-ast.svg?branch=master