A tolerant JSON parser


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...
*/
`

Install

`shell
npm install json-ast
`

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.js.

API


`javascript
import {parse, Visitor, AST} from 'json-ast';

// The visitor can stop at any time by assigning Visitor.stop = true
class MyVisitor extends Visitor {
constructor() {
super();
this.comments = [];
}

comment(commentNode) {
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 AST.JsonDocument);

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

// One can also the JsonNode.toJSON static method to convert to a JavaScript object
const obj = JsonNode.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