flatted

What is flatted?

The flatted npm package is a library for encoding and decoding JavaScript objects into a flat JSON format. It is particularly useful for handling circular references and complex data structures that JSON.stringify cannot handle by default.

What are flatted's main functionalities?

Encoding objects with circular references

Flatted allows you to encode objects that have circular references, which would throw an error with JSON.stringify. For example, if you have an object 'circularObj' that references itself, you can use flatted.stringify(circularObj) to get a string representation of the object.

{"encoded": "flatted.stringify(circularObj)"}

Decoding flatted strings back to objects

After encoding an object with circular references using flatted, you can decode the resulting string back into an object with flatted.parse(flattedString). This will restore the circular references and give you back the original object structure.

{"decoded": "flatted.parse(flattedString)"}

Other packages similar to flatted

circular-json

CircularJSON is a JSON-like format that can encode circular structures and other complex data types. It is similar to flatted but was superseded by flatted due to its ability to handle more data types and its smaller footprint.

json-stringify-safe

json-stringify-safe is a package that can stringify objects with circular references without throwing. It works by replacing circular references with a string '[Circular]'. It is similar to flatted but does not allow for reconstruction of the original object with circular references.

README

flatted

A fast and minimal circular JSON parser.

Usable via CDN or as regular module.

// ESM
import {parse, stringify} from 'flatted/esm';

// CJS
const {parse, stringify} = require('flatted/cjs');

const a = [{}];
a[0].a = a;
a.push(a);

stringify(a); // [["1","0"],{"a":"0"}]

Compatibility

All ECMAScript engines compatible with Map, Set, Object.keys, and Array.prototype.reduce will work, even if polyfilled.

How does it work ?

While stringifying, all Objects, including Arrays, and strings, are flattened out and replaced as unique index. *

Once parsed, all indexes will be replaced through the flattened collection.

^{_{* represented as string to avoid conflicts with numbers}}

// logic example
var a = [{one: 1}, {two: '2'}];
a[0].a = a;
// a is the main object, will be at index '0'
// {one: 1} is the second object, index '1'
// {two: '2'} the third, in '2', and it has a string
// which will be found at index '3'

Flatted.stringify(a);
// [["1","2"],{"one":1,"a":"0"},{"two":"3"},"2"]
// a[one,two]    {one: 1, a}    {two: '2'}  '2'

Why not CircularJSON ?

If approved by the community, this project will be the core of CircularJSON V2.

The main reasons for having this software a part are:

• battle-testing against all complex cases before releasing CircularJSON V2
• provide a minimal parser without extra complexity needed by revivers and replacers
• give developers a way to compare the two formats (on average, with big structures, smaller with flatted)

Once satisfied by feedbacks and results, there will be a version of this project fully compatible with JSON API.