json-web3

BigInt-safe JSON serialization and deserialization for Web3 data.

Install

pnpm add json-web3
# or
npm i json-web3
# or
yarn add json-web3

Usage

import jsonWeb3 from 'json-web3'

const payload = {
  balance: 1234567890123456789n,
  decimals: 18n,
  u8Array: new Uint8Array([1, 2, 3, 255]),
  u16Array: new Uint16Array([1, 2, 3, 255]),
  bigIntArray: new BigInt64Array([18446744073709551615n, 2n, 3n, 255n]),
  createdAt: new Date('2020-01-02T03:04:05.006Z'),
  ids: new Set([123, 456]),
  headers: new Map([['hello', 'world']]),
  re: /([^\s]+)/g,
  url: new URL('https://example.com/'),
  fn: function echo(arg) {
    return arg
  },
}

const text = jsonWeb3.stringify(payload)
// => {"balance":{"__@json.bigint__":"1234567890123456789"},"decimals":{"__@json.bigint__":"18"},"u8Array":{"__@json.typedarray__":{"type":"Uint8Array","bytes":"0x010203ff"}},"u16Array":{"__@json.typedarray__":{"type":"Uint16Array","bytes":"0x010002000300ff00"}},"bigIntArray":{"__@json.typedarray__":{"type":"BigInt64Array","bytes":"0xffffffffffffffff02000000000000000300000000000000ff00000000000000"}}}

const restored = jsonWeb3.parse(text)
/* =>
  {
    balance: 1234567890123456789n,
    decimals: 18n,
    u8Array: Uint8Array(4) [1, 2, 3, 255]...,
    u16Array: Uint16Array(4)...,
    bigIntArray: BigInt64Array(4)...,
    createdAt: Date(...),
    ids: Set(2) {...},
    headers: Map(1) {...},
    re: /([^\s]+)/g,
    url: URL(...),
    fn: undefined
  }
*/

const textUnsafe = jsonWeb3.stringify_UNSAFE(payload)
const restoredUnsafe = jsonWeb3.parse_UNSAFE(textUnsafe)
// restoredUnsafe.fn is a callable function

Full example

import jsonWeb3 from 'json-web3'

window.JSON = jsonWeb3 // Yes, you can replace it directly; it is fully compatible.

API (Fully compatible with native globalThis.JSON)

• stringify(value, replacer?, space?)
• parse(text, reviver?)
• stringify_UNSAFE(value, replacer?, space?) (serializes Function payloads)
• parse_UNSAFE(text, reviver?) (revives Function payloads via new Function(...))

Type support

type	supported by standard JSON?	supported by json-web3?
string	✅	✅
number	✅	✅
boolean	✅	✅
null	✅	✅
Array	✅	✅
Object	✅	✅
undefined	❌	❌
Infinity	❌	✅
-Infinity	❌	✅
NaN	❌	✅
BigInt	❌	✅
Date	❌	✅
RegExp	❌	✅
Set	❌	✅
Map	❌	✅
URL	❌	✅
ArrayBuffer	❌	✅
Uint8Array	❌	✅
Uint8ClampedArray	❌	✅
Uint16Array	❌	✅
Uint32Array	❌	✅
Int8Array	❌	✅
Int16Array	❌	✅
Int32Array	❌	✅
Float16Array	❌	✅
Float32Array	❌	✅
Float64Array	❌	✅
BigInt64Array	❌	✅
BigUint64Array	❌	✅
Function	❌	✅ ⚠️(use UNSAFE api, it's dangerous)

Note

• bigint values are encoded as objects: {"__@json.bigint__":"<value>"}.
• Non-finite numbers (NaN, Infinity, -Infinity) are encoded as {"__@json.number__":"<value>"}.
• Date values are encoded as {"__@json.date__":<timestamp>}.
• Map values are encoded as {"__@json.map__":[[k,v],...]} and Set values as {"__@json.set__":[...]}.
• RegExp values are encoded as {"__@json.regexp__":{"source":"...","flags":"..."}}.
• URL values are encoded as {"__@json.url__":"..."}.
• Function values are encoded as {"__@json.function__":"<source>"} by stringify_UNSAFE and are only revived by parse_UNSAFE using new Function(...) (using the UNSAFE function pair is dangerous; make sure your data is trusted).
• ArrayBuffer values are encoded as {"__@json.arraybuffer__":{"bytes":"0x..."}} and decoded back to ArrayBuffer.
• Node Buffer JSON shapes and typed arrays are encoded as {"__@json.typedarray__":{"type":"<Name>","bytes":"0x..."}} and decoded back to the original typed array (Uint8Array, Uint8ClampedArray, Uint16Array, Uint32Array, Int8Array, Int16Array, Int32Array, Float32Array, Float64Array, BigInt64Array, BigUint64Array).

Compared to libraries that require eval-based parsing (for example, serialize-javascript), this approach is generally safer and more efficient.

RFC (Serialization Format)

To enable cross-language interoperability, the serialization format is specified in RFC.md. It defines the canonical tag objects, payload shapes, validation rules, and UNSAFE function handling.