fast-stringify

A tiny, blazing fast stringifier that safely handles circular objects

Table of contents

• fast-stringify
  • Table of contents
  • Summary
  • Usage
    • stringify
  • Importing
  • Benchmarks
    • Simple objects
    • Complex objects
    • Circular objects
    • Special objects
  • Development

Summary

The fastest way to stringify an object will always be the native JSON.stringify, but it does not support circular objects out of the box. If you need to stringify objects that have circular references, fast-stringify is there for you! It maintains a very similar API to the native JSON.stringify, and aims to be the most performant stringifier that handles circular references.

Usage

import stringify from 'fast-stringify';
 
const object = {
  foo: 'bar',
  deeply: {
    recursive: {
      object: {},
    },
  },
};
 
object.deeply.recursive.object = object.deeply.recursive;
 
console.log(stringify(object));
// {"foo":"bar","deeply":{"recursive":{"object":"[ref=.deeply.recursive]"}}}

stringify

type StandardReplacer = (key: string, value: any) => any;
type CircularReplacer = (key: string, value: any, referenceKey: string) => any;
 
function stringify(
  value: any,
  replacer?: StandardReplacer,
  indent?: number,
  circularReplacer: CircularReplacer,
): string;

Stringifies the object passed based on the parameters you pass. The only required value is the object. The additional parameters passed will customize how the string is compiled.

• value => the value to stringify
• replacer => function to customize how the non-circular value is stringified (see the documentation for JSON.stringify for more details)
• indent => number of spaces to indent the stringified object for pretty-printing (see the documentation for JSON.stringify for more details)
• circularReplacer => function to customize how the circular value is stringified (defaults to [ref=##] where ## is the referenceKey)
  • referenceKey is a dot-separated key list reflecting the nested key the object was originally declared at

Importing

// ESM in browsers
import stringify from 'fast-stringify';
 
// ESM in NodeJS
import stringify from 'fast-stringify/mjs';
 
// CommonJS
const stringify = require('fast-stringify');

Benchmarks

Simple objects

Small number of properties, all values are primitives

	Operations / second	Relative margin of error
fast-stringify	598,072	0.59%
fast-json-stable-stringify	339,082	0.86%
json-stringify-safe	333,447	0.46%
json-stable-stringify	255,619	0.71%
json-cycle	194,553	0.60%
decircularize	141,821	1.35%

Complex objects

Large number of properties, values are a combination of primitives and complex objects

	Operations / second	Relative margin of error
fast-stringify	97,559	0.32%
json-stringify-safe	59,948	0.44%
fast-json-stable-stringify	57,656	1.14%
json-cycle	51,892	0.59%
json-stable-stringify	39,180	1.01%
decircularize	27,047	0.84%

Circular objects

Objects that deeply reference themselves

	Operations / second	Relative margin of error
fast-stringify	87,030	0.51%
json-stringify-safe	56,329	0.49%
json-cycle	48,116	0.77%
decircularize	25,240	0.68%
fast-json-stable-stringify (not supported)	0	0.00%
json-stable-stringify (not supported)	0	0.00%

Special objects

Custom constructors, React components, etc

	Operations / second	Relative margin of error
fast-stringify	24,250	0.38%
json-stringify-safe	19,526	0.52%
json-cycle	18,433	0.74%
fast-json-stable-stringify	18,202	0.73%
json-stable-stringify	13,041	0.87%
decircularize	9,175	0.82%

Development

Standard practice, clone the repo and npm i to get the dependencies. The following npm scripts are available:

• benchmark => run benchmark tests against other equality libraries
• build => build dist files with rollup
• clean => run clean:dist and clean:mjs scripts
• clean:dist => run rimraf on the dist folder
• clean:mjs => run rimraf on the mjs folder
• copy:mjs => copy and transform the ESM file generated by dist to be consumable as an .mjs file
• dev => start webpack playground App
• dist => run clean, build, and copy:mjs scripts
• lint => run ESLint on all files in src folder (also runs on dev script)
• lint:fix => run lint script, but with auto-fixer
• prepublishOnly => run lint, typecheck, test:coverage, and dist scripts
• release => run release-it for standard versions (expected to be installed globally)
• release:beta => run release-it for beta versions (expected to be installed globally)
• start => run dev
• test => run Jest with NODE_ENV=test on all files in __tests__ folder
• test:coverage => run same script as test with code coverage calculation
• test:watch => run same script as test but keep persistent watcher
• typecheck => run TypeScript types validation