@ublitzjs/niche-json-stringify - fastest pre-optimised niche JSON.stringify alternative

A blazing-fast, preoptimising stringifier generator, designed to outpace JSON.stringify in Web on both frontend and backend, while being type-safe and still handling all character escaping.

Inspired by fast-json-stringify and compile-json-stringify. As in compile-json-stringify, niche-json-stringify uses JSONSchema to define the input type, unlike fast-json-stringify. However, it handles only the most popular cases, that's why it is "niche".

Features

• No Dependencies: Works in NodeJS, Bun and a Web browser
• The fastest for small payloads: "niche" approach helped achieve these results. See benchmarks
• Comparable speed with JSON.stringify for large payloads: in NodeJS for non-escaped strings and in Bun for both
• TypeScript-first
• Prebuilt for ESM and CJS
• Thoroughly tested

---

Benchmarks

• NodeJS
• Bun

Installation

bun add @ublitzjs/niche-json-stringify

Quick start

Generate a specialized serializer from a JSON Schema (or a TypeBox schema). The generated function does not validate its input - it assumes the data already matches the schema.

import { Type } from "@sinclair/typebox";
import { createStringify } from "@ublitzjs/niche-json-stringify";

const User = Type.Object({
  id: Type.Integer(),
  name: Type.String(),
  admin: Type.Optional(Type.Boolean({ default: false })),
  tags: Type.Array(Type.String(), { default: [] }),
});

const stringify = createStringify(User);

const json = stringify({
  id: 1,
  name: "Alice",
});

console.log(json);
// {"id":1,"name":"Alice","admin":false,"tags":[]}

Default values

Schemas may define a default value for any supported type. If the corresponding property is undefined, the generated serializer emits the default instead.

const Config = Type.Object({
  host: Type.String({ default: "localhost" }),
  port: Type.Integer({ default: 3000 }),
  tls: Type.Boolean({ default: false }),
  retries: Type.Integer({ default: 3 }),
});

const stringify = createStringify(Config);

stringify({});
// {"host":"localhost","port":3000,"tls":false,"retries":3}

Unsafe strings

By default, all string values are JSON-escaped.

If you know a string is already safe (contains no characters requiring escaping), mark it with format: "unsafe" to skip escaping.

const LogEntry = Type.Object({
  timestamp: Type.String({ format: "unsafe" }),
  level: Type.String({ format: "unsafe" }),
  message: Type.String(), // escaped
});

const stringify = createStringify(LogEntry);

Additional properties

additionalProperties is supported. Unknown properties are serialized using JSON.stringify. However, it does not work with default values or with and outer object - only properties.

const Payload = Type.Object({
  id: Type.Integer(),
  extra: Type.Object({}, { additionalProperties: true }) 
});

const stringify = createStringify(Payload);

stringify({
  id: 1,
  extra: { hello: "world" },
});
// {"id":1,"extra":{"hello":"world"}}

Custom string escaping

By default, createStringify() uses the escaping implementation from fast-json-stringify.

You can supply another escaping function, for example the one from compile-json-stringify:

import {
  createStringify,
  CJSescape,
} from "@ublitzjs/niche-json-stringify";

const stringify = createStringify(User, CJSescape);

Specialized array serializers

For hot paths, the package also exports highly optimized serializers for common array types. Internally they are used when array has certain size and replaced with JSON.stringify when fed a huge one.

import {
  num_arr_node,
  num_arr_bun,
  bool_arr_bun,
  bool_arr_node,
  str_arr_node,
  str_arr_bun,
} from "@ublitzjs/niche-json-stringify";

int_arr_node([1, 2, 3]);
int_arr_bun([1, 2, 3]);
// "[1,2,3]"

// look for use cases
bool_arr_node([true, false]);
bool_arr_bun([true, false]);
// "[true,false]"

// optimised non-escaping serialisers
str_arr_node(["a", "b"]);
str_arr_bun(["a", "b"]);
// "[\"a\",\"b\"]"

Note: Generated serializers prioritize speed over safety. They do not validate input, so invalid data may produce invalid JSON or incorrect output. Validate your data before serialization if necessary.