json

JSON Parser Example

A JSON parser built with @prostojs/parser. Parses JSON strings into JavaScript values — output is built incrementally via hooks, no post-parse tree walk.

Usage

import { parseJson } from './src/json-parser'

parseJson('{"name": "Alice", "age": 30}')
// { name: 'Alice', age: 30 }

parseJson('[1, true, null, "hello"]')
// [1, true, null, 'hello']

parseJson('42')
// 42

How It Works

Four nodes handle the JSON grammar:

Node	Start	End	Purpose
string	"	"	String values (with escape processing)
array	[	]	Arrays — children for nested values, onContent for bare primitives
object	{	}	Objects — strings as keys or values, onContent for primitive values
root	(none)	EOF	Top-level wrapper

Key Design Decisions

• Bare primitives (numbers, booleans, null) are not delimited by tokens, so they appear as text content. The onContent hook splits text on commas and parses each part.
• Key/value disambiguation in objects uses state tracking (pendingKey / awaitingValue) — when a string child arrives and we're not awaiting a value, it's a key; otherwise it's a value.
• Escape sequences (\n, \t, \uXXXX, etc.) are processed in the string node's onClose hook.

Architecture

root
 └── recognizes: string, array, object
      array  → recognizes: string, array, object
      object → recognizes: string, array, object

Output is assembled during parsing:

• array.onContent → split comma-separated text into primitives, push to data.items
• array.onChild → push child value to data.items
• object.onChild → alternate between key and value assignment
• object.onContent → parse primitive values after : for the pending key