destr

What is destr?

The `destr` npm package is designed to safely parse JSON strings without throwing an error for invalid JSON. It can return the original string if parsing fails, making it useful for handling dynamic JSON data that may not always be properly formatted. It also recognizes and correctly parses values like `null`, `true`, `false`, and `undefined`.

What are destr's main functionalities?

Safe JSON parsing

Safely parse a JSON string without throwing an error. If the string is not valid JSON, it returns the original string.

"const destr = require('destr');
const json = '{\"key\":\"value\"}';
const parsed = destr(json);
console.log(parsed); // Output: { key: 'value' }"

Parsing special JSON values

Correctly parse special JSON values such as `null`, `true`, `false`, and `undefined`, returning their corresponding JavaScript types.

"const destr = require('destr');
console.log(destr('null')); // Output: null
console.log(destr('true')); // Output: true
console.log(destr('false')); // Output: false
console.log(destr('undefined')); // Output: undefined"

Other packages similar to destr

json5

Similar to `destr`, `json5` allows for parsing of JSON data with more lenient syntax rules, such as trailing commas and comments. However, `json5` focuses on extending JSON syntax to be more flexible, while `destr` focuses on safe parsing and handling special values.

safe-json-parse

This package offers functionality similar to `destr` by providing a safe way to parse JSON strings without throwing errors for invalid JSON. The main difference is in the API and specific handling of non-JSON values.

README

destr

A faster, secure and convenient alternative for JSON.parse.

Usage

Node.js

Install dependency:

# npm
npm i destr

# yarn
yarn add destr

# pnpm
pnpm i destr

Import into your Node.js project:

// ESM
import { destr, safeDestr } from "destr";

// CommonJS
const { destr, safeDestr } = require("destr");

Deno

import { destr, safeDestr } from "https://deno.land/x/destr/src/index.ts";

console.log(destr('{ "deno": "yay" }'));

Why?

✅ Type Safe

const obj = JSON.parse("{}"); // obj type is any

const obj = destr("{}"); // obj type is unknown by default

const obj = destr<MyInterface>("{}"); // obj is well-typed

✅ Fast fallback to input if is not string

🚀 Up to 500 faster than JSON.parse!

// Uncaught SyntaxError: Unexpected token u in JSON at position 0
JSON.parse();

// undefined
destr();

✅ Fast lookup for known string values

🚀 Up to 900 times faster than JSON.parse!

// Uncaught SyntaxError: Unexpected token T in JSON at position 0
JSON.parse("TRUE");

// true
destr("TRUE");

✅ Fallback to original value if parse fails (empty or any plain string)

🚀 Up to 900 times faster than JSON.parse!

// Uncaught SyntaxError: Unexpected token s in JSON at position 0
JSON.parse("salam");

// "salam"
destr("salam");

Note: This fails in safe/strict mode with safeDestr.

✅ Avoid prototype pollution

const input = '{ "user": { "__proto__": { "isAdmin": true } } }';

// { user: { __proto__: { isAdmin: true } } }
JSON.parse(input);

// { user: {} }
destr(input);

✅ Strict Mode

When using safeDestr it will throw an error if the input is not a valid JSON string or parsing fails. (non string values and built-ins will be still returned as-is)

// Returns "[foo"
destr("[foo");

// Throws an error
safeDestr("[foo");

Benchmarks

Locally try with pnpm benchmark. Below are esults on Node.js v18.16.0 with MBA M2.

Note destr is sometimes little bit slower than JSON.parse when parsing a valid JSON string mainly because of transform to avoid prototype pollution which can lead to serious security issues if not being sanitized. In the other words, destr is better when input is not always a json string or from untrusted source like request body.

=== Non-string fallback ==
JSON.parse x 9,498,532 ops/sec ±0.57% (96 runs sampled)
destr x 153,323,211 ops/sec ±0.13% (99 runs sampled)
safeDestr x 64,237,062 ops/sec ±0.22% (96 runs sampled)
sjson:
@hapi/bourne x 9,190,459 ops/sec ±0.50% (93 runs sampled)
Fastest is destr

=== Known values ==
JSON.parse x 14,260,909 ops/sec ±0.54% (95 runs sampled)
destr x 72,916,945 ops/sec ±0.15% (98 runs sampled)
safeDestr x 36,544,906 ops/sec ±0.31% (98 runs sampled)
sjson x 11,157,730 ops/sec ±0.53% (96 runs sampled)
@hapi/bourne x 13,241,853 ops/sec ±0.73% (93 runs sampled)
Fastest is destr

=== plain string ==
JSON.parse (try-catch) x 10,603,912 ops/sec ±0.75% (91 runs sampled)
destr x 82,123,481 ops/sec ±2.37% (99 runs sampled)
safeDestr x 40,737,935 ops/sec ±0.97% (96 runs sampled)
sjson (try-catch) x 9,194,305 ops/sec ±1.96% (94 runs sampled)
@hapi/bourne x 10,816,232 ops/sec ±1.59% (90 runs sampled)
Fastest is destr

=== package.json ==
JSON.parse x 403,428 ops/sec ±0.31% (101 runs sampled)
destr x 338,668 ops/sec ±0.27% (97 runs sampled)
safeDestr x 335,756 ops/sec ±0.29% (98 runs sampled)
sjson x 355,493 ops/sec ±0.15% (101 runs sampled)
@hapi/bourne x 384,948 ops/sec ±0.24% (98 runs sampled)
Fastest is JSON.parse

=== broken object ==
JSON.parse (try-catch) x 406,262 ops/sec ±0.18% (100 runs sampled)
destr x 337,602 ops/sec ±0.37% (99 runs sampled)
safeDestr x 320,071 ops/sec ±0.35% (97 runs sampled)
sjson (try-catch) x 326,689 ops/sec ±0.41% (97 runs sampled)
@hapi/bourne x 313,024 ops/sec ±0.91% (94 runs sampled)
Fastest is JSON.parse (try-catch)

License

MIT. Made with 💖

Changelog

v2.0.1

compare changes

🔥 Performance

• Avoid lowercasing long strings (#81)

📖 Documentation

• Correct safeDestr example usage and tests (#75)

🏡 Chore

• Update dependencies (46c3915)
• Add autofix ci (ad69b83)

🎨 Styles

• Format code (5e014f9)

❤️ Contributors

• Pooya Parsa (@pi0)
• Webstrand [e-mail]
• Frenco [e-mail]