Note: This repository resolves several performance issues and updates dependent packages. There are no plans to add new features.

A tolerant JSON parser

!Test

Install

``shell
npm install @anchan828/json-ast
`

Features

The original code was developed by Vlad Trushin. Breaking modifications were made by Romain Gaucher to create a less strict JSON parser. Additionally, a more typical interaction with the AST has been implemented.

Current modifications and features as of 2.1.6 include:

- Creation of a JsonDocument root node and more formal AST structure
- Support for inline comments
- Support for multi-line comments
- Support for trailing commas and many consecutive commas
- Include visitor pattern to visit the AST
- Include a limited error-recovery mode trying to catch (when junker set to true):
- unclosed objects or arrays
- too many closing braces or brackets
- automatic comma injection
- support for unquoted keys
- Conversion to a native JavaScript object from JsonNode

Basic examples are available to show how to use this package.

JSONish

The JSON parser accepts a superset of the JSON language:

`json
// some comment
{
"key1": "value1", // some other comments
"key2": "value2",
,
,
/*
Oh dear! It's important to put this here.
And we love commas too!
And we're missing the closing brace...
*/
`

Structure of the AST

As of 2.1.0, the AST is defined with the following types:

`javascript
[JsonNode] // Essentially an abstract class
position: [Position]

[JsonDocument] extends [JsonNode]
child: [?]*
comments: [JsonComment]*

[JsonValue] extends [JsonNode]
value: [?]

[JsonObject] extends [JsonNode]
properties: [JsonProperty]*
comments: [JsonComment]*

[JsonProperty] extends [JsonNode]
key: [JsonKey]
value: [?]*

[JsonKey] extends [JsonValue]

[JsonArray]
items: *
comments: [JsonComment]*

[JsonComment] extends [JsonValue]
[JsonString] extends [JsonValue]
[JsonNumber] extends [JsonValue]
[JsonTrue] extends [JsonValue]
[JsonFalse] extends [JsonValue]
[JsonNumber] extends [JsonValue]
`

All the types exists in src/ast.ts.

API

`javascript
import { parse, Visitor, toJSON } from "json-ast";

// The visitor can stop at any time by assigning Visitor.stop = true
class MyVisitor extends Visitor {
private comments: string[] = []

public comment(commentNode: JsonComment): void {
this.comments.push(commentNode.value);
}
}

const JSON_BUFFER = // Some comment
{
"key": "value"
;

// verbose will include the position in each node
const ast = parse(JSON_BUFFER, { verbose: true, junker: true });
assert(ast instanceof JsonDocument);

const visitor = new MyVisitor();
visitor.visit(ast);
assert.deepEqual(visitor.comments, [" Some comment"]);

// One can also the toJSON(JsonNode) static method to convert to a JavaScript object
const obj = toJSON(ast);
assert(obj.key === "value");
`

$3

The second argument of the parse function takes an object with the following settings:

- verbose: include positions in each AST node, true by default
- junker: enables an error recovery mode, false` by default

License

MIT Vlad Trushin and Romain Gaucher and anchan828