Fix malformed JSON strings that have been through multiple stringify operations.

JSON-Parsefy intelligently parses deeply nested stringified JSON data, automatically converting escaped strings back to proper JSON objects and arrays. Perfect for handling data from APIs, databases, or any source that has been over-stringified.

When JSON data goes through multiple JSON.stringify() operations, it becomes deeply escaped and unreadable:

// Original data
const user = {
  name: "John Doe",
  age: 30,
  location: { city: "New York", geo: { lat: 40.7128, lng: -74.0060 } }
};

// After multiple stringify operations
const malformed = "{\"name\":\"John Doe\",\"age\":\"30\",\"location\":\"{\\\"city\\\":\\\"New York\\\",\\\"geo\\\":\\\"{\\\\\\\"lat\\\\\\\":40.7128,\\\\\\\"lng\\\\\\\":-74.0060}\\\"}\"}";

// This fails with JSON.parse()
JSON.parse(malformed); // ❌ Error: Unexpected token

JSON-Parsefy automatically detects and fixes these issues:

import { Parsefy } from "json-parsefy";

const fixed = Parsefy.this(malformed);
console.log(fixed);
// ✅ { name: "John Doe", age: 30, location: { city: "New York", geo: { lat: 40.7128, lng: -74.0060 } } }

npm install json-parsefy
# or
yarn add json-parsefy
# or
pnpm add json-parsefy

import { Parsefy } from "json-parsefy";

const malformedJson = `{"name":"John","data":"{\\"items\\":[1,2,3],\\"active\\":true}"}`;

const result = Parsefy.this(malformedJson);
// Result: { name: "John", data: { items: [1,2,3], active: true } }

For automatic parsing in class properties, you can use the decorator feature. This requires installing class-transformer as a peer dependency:

npm install class-transformer
# or
yarn add class-transformer
# or
pnpm add class-transformer

import { plainToClass } from "class-transformer";
import { JSONFlattener } from "json-parsefy";

class User {
  @JSONFlattener()
  profile: any; // Will be automatically parsed if it's a string
}

const userData = {
  profile: '{"name":"John","settings":"{\\"theme\\":\\"dark\\"}"}'
};

const user = plainToClass(User, userData);
console.log(user.profile);
// Result: { name: "John", settings: { theme: "dark" } }

Note: The decorator feature is optional. If you don't install class-transformer, the decorator will display a warning and act as a no-op, but your main parsing functionality will still work perfectly.

// Common scenario: API returns over-stringified data
const apiResponse = `{
  "user": "{\\"id\\":123,\\"name\\":\\"John\\",\\"preferences\\":\\"{\\\\\\"theme\\\\\\":\\\\\\"dark\\\\\\"}\\"}",
  "status": "success"
}`;

const cleanData = Parsefy.this(apiResponse);
// Result: { user: { id: 123, name: "John", preferences: { theme: "dark" } }, status: "success" }

// Database stores JSON as escaped strings
const dbRecord = {
  id: 1,
  metadata: '{"tags":"[\\"urgent\\",\\"important\\"]","config":"{\\"notifications\\":true}"}'
};

const parsed = Parsefy.this(JSON.stringify(dbRecord));
// Result: { id: 1, metadata: { tags: ["urgent", "important"], config: { notifications: true } } }

const complexData = `{
  "user": "{\\"profile\\":\\"{\\\\\\"name\\\\\\":\\\\\\"John\\\\\\",\\\\\\"settings\\\\\\":\\\\\\"{\\\\\\\\\\\\\\"theme\\\\\\\\\\\\\\":\\\\\\\\\\\\\\"dark\\\\\\\\\\\\\\"}\\\\\\"}\\"}",
  "permissions": "{\\"admin\\":true,\\"roles\\":\\"[\\\\\\"user\\\\\\",\\\\\\"editor\\\\\\"]\\"}"
}`;

const result = Parsefy.this(complexData);
// Result: { 
//   user: { profile: { name: "John", settings: { theme: "dark" } } },
//   permissions: { admin: true, roles: ["user", "editor"] }
// }

• 🔄 Smart Detection: Automatically identifies stringified JSON within strings
• 🌳 Deep Parsing: Handles unlimited nesting levels using BFS algorithm
• 🛡️ Type Safe: Full TypeScript support with proper type definitions
• ⚡ Performance: Optimized parsing with minimal overhead
• 🎯 Optional Decorator Support: Seamless integration with class-transformer (when installed)
• 🧪 Well Tested: Comprehensive test coverage with edge cases
• 📦 Minimal Dependencies: Lightweight with optional peer dependencies

JSON-Parsefy uses a two-step process:

1. Recursive Parsing: Continuously parses stringified JSON until no more parsing is possible
2. BFS Traversal: Uses breadth-first search to systematically process all nested objects and arrays

This approach ensures that even deeply nested and multiply-escaped JSON strings are properly restored to their original structure.

Main parsing function that takes a malformed JSON string and returns a properly structured object.

Parameters:

• jsonString: The malformed JSON string to parse

Returns:

• Properly structured JavaScript object

Throws:

• Error if the input is not a valid JSON string

Class property decorator that automatically parses stringified JSON values. Requires class-transformer as a peer dependency.

Usage:

class MyClass {
  @JSONFlattener()
  jsonField: any;
}

Note: If class-transformer is not installed, the decorator will log a warning and act as a no-op decorator.

git clone https://github.com/DMBerlin/json-parsefy.git
cd json-parsefy
pnpm install

pnpm build          # Build the project
pnpm test           # Run tests
pnpm test:watch     # Run tests in watch mode
pnpm test:cov       # Run tests with coverage
pnpm lint           # Run linter

Contributions are welcome! Please read our Contributing Guidelines for details.

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Make your changes
4. Run tests (pnpm test)
5. Commit your changes
6. Push to your branch (git push origin feature/amazing-feature)
7. Open a Pull Request

This project is licensed under the ISC License - see the LICENSE file for details.

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• 💬 Discussions
• 📧 Contact

Made with ❤️ by Daniel Marinho