Parse JSON into CST (Concrete Syntax Tree)
npm install json-cst[![npm version][npm-image]][npm-url]
[![downloads][downloads-image]][npm-url]
[![build status][build-image]][build-url]
[![coverage status][coverage-image]][coverage-url]
[![Language grade: JavaScript][lgtm-image]][lgtm-url]
This package parses a JSON into CST (Concrete Syntax Tree), similar to an AST but more low-level and with ties to the lexer tokens. It uses json-lexer to parse the file into tokens. The speed is practically the same as json-to-ast (it's ~10% faster than json-to-ast), but it's far smaller (even including json-lexer). Pure package is 7x smaller, install size 12x smaller, bundling it makes it 6x smaller according to bundlephobia (json-to-ast vs json-cst).
It comes with TypeScript typings.
npm i json-cst or yarn add json-cst
This is a [pure ESM][pure-esm] package, and requires Node.js >=14.13.1
The package exports parse(json: string, options: ParseCstOptions): CstNode.
options is an optional object which can contain includeValueTokens: true to include the value tokens in the result, meaning, for objects and arrays, they will include the slice of tokens for the beginning and end of the object/array.
The tokens are parsed into a hierarchy of nodes, each with a "kind" property:
``ts`
type CstKindLiteral = 'literal'; // null, true, false
type CstKindNumber = 'number';
type CstKindString = 'string';
type CstKindObjectPropertyColon = 'object-property-colon';
type CstKindObjectProperty = 'object-property';
type CstKindObject = 'object';
type CstKindArrayElement = 'array-element';
type CstKindArray = 'array';
And the CstNode returned by parse() is a CstValueNode, i.e. one of:
- CstNodeLiteral
-
-
-
-
Other nodes are:
- CstNodeObjectProperty
-
-
Each token contain a { range: CstTokenRange } where
`ts`
interface CstTokenRange {
start: number;
end: number;
}
Each of the primitive tokens CstNodeLiteral, CstNodeNumber and CstNodeString contain { token: Token } being the raw token from json-lexer.
Object and array tokens CstNodeObject and CstNodeArray contain a property children being an array of either CstNodeObjectProperty or CstNodeArrayElement.
A CstNodeObjectProperty has a keyToken property being the lexer token for the property name, and a valueNode being a CstNode. A CstNodeArrayElement also has a valueNode.
See types.ts` for exact typings.
[npm-image]: https://img.shields.io/npm/v/json-cst.svg
[npm-url]: https://npmjs.org/package/json-cst
[downloads-image]: https://img.shields.io/npm/dm/json-cst.svg
[build-image]: https://img.shields.io/github/workflow/status/grantila/json-cst/Master.svg
[build-url]: https://github.com/grantila/json-cst/actions?query=workflow%3AMaster
[coverage-image]: https://coveralls.io/repos/github/grantila/json-cst/badge.svg?branch=master
[coverage-url]: https://coveralls.io/github/grantila/json-cst?branch=master
[lgtm-image]: https://img.shields.io/lgtm/grade/javascript/g/grantila/json-cst.svg?logo=lgtm&logoWidth=18
[lgtm-url]: https://lgtm.com/projects/g/grantila/json-cst/context:javascript
[pure-esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c