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 💖

webstrand/destr