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

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

// undefined
destr();

✅ Fast lookup for known string values

// 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)

// 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

destr is faster generally for arbitrary inputs but also 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.

Check Benchmark Results or run with pnpm run bench:node or pnpm run bench:bun yourself!

License

MIT. Made with 💖

Changelog

v2.0.3

compare changes

🩹 Fixes

• Improve compatibility with runtimes not supporting String.prototype.at() (#102)

🏡 Chore

• Update lockfile (930fe7b)
• Update bench (d0a83f9)
• Update readme (72a5c5c)
• Lint (ae61652)

✅ Tests

• Test with node 20 (a33a2e1)

❤️ Contributors

• Pooya Parsa (@pi0)
• Allenyu (@AllenYu0118)