# u-node

> A library to compactly encode data which can be used in URL.

Latest version **0.0.8** (published 2026-05-01) · MIT license · 0 weekly downloads

## Install

```sh
npm install u-node
pnpm add u-node
yarn add u-node
bun add u-node
```

## Health

**Score 60/100 (C)** — status: stable.

Positive: has types; esm support; no vulnerabilities; high quality score.

Warnings: low downloads; pre 1.0.

## Facts

| | |
|---|---|
| Version | 0.0.8 |
| Published | 2026-05-01 |
| First published | 2016-02-14 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Node | >=24 |
| Dependencies | 0 |
| Unpacked size | 62.2 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 177 |
| Author | ananthakumaran |
| Maintainers | ananthakumaran |
| Keywords | url, encode, compression |

## Links

- npm: https://www.npmjs.com/package/u-node
- Repository: https://github.com/ananthakumaran/u
- Homepage: https://github.com/ananthakumaran/u#readme
- Issues: https://github.com/ananthakumaran/u/issues
- npm.io page: https://npm.io/package/u-node

## Alternatives

- [base64url](https://npm.io/package/base64url.md) — 6.1M weekly downloads
- [get-installed-path](https://npm.io/package/get-installed-path.md) — 502.9K weekly downloads
- [@uppy/url](https://npm.io/package/@uppy/url.md) — 185.8K weekly downloads
- [@d3fc/d3fc-shape](https://npm.io/package/@d3fc/d3fc-shape.md) — 16.2K weekly downloads
- [localizer](https://npm.io/package/localizer.md) — 226 weekly downloads

## Recent versions

- 0.0.8 (latest) — 2026-05-01
- 0.0.7 — 2026-05-01
- 0.0.6 — 2026-05-01
- 0.0.5 — 2026-05-01
- 0.0.4 — 2026-05-01
- 0.0.3 — 2026-04-27
- 0.0.2 — 2016-02-14
- 0.0.1 — 2016-02-14

## README

# μ

Without μ:
`http://app.com/url#%7B%22lookingFor%22:%22bride%22,%22age%22:%5B25,30%5D,%22religion%22:%22Hindu%22,%22motherTongue%22:%22Bengali%22,%22onlyProfileWithPhoto%22:true%7D`

With μ:
`http://app.com/url#bHhc9I-aqa`

μ is a JavaScript library for encoding/decoding state (JavaScript
object) in URL. Define a spec for the state, based on which the
encoding is done. Manage the state with versioning.

## Example

Import the library

```javascript
import { fromJson, encode, decode } from "u-node";
```

Define the spec.

```javascript
const spec = {
  lookingFor: ["oneOf", "bride", "groom"],
  age: ["tuple", ["integer"] /* min */, ["integer"] /* max */],
  religion: ["oneOf", "Hindu", "Muslim", "Christian", "Sikh", "Parsi", "Jain", "Buddhist", "Jewish", "No Religion", "Spiritual", "Other" ],
  motherTongue: ["oneOf", "Assamese", "Bengali", "English", "Gujarati", "Hindi", "Kannada", "Konkani", "Malayalam", "Marathi", "Marwari", "Odia", "Punjabi", "Sindhi", "Tamil", "Telugu", "Urdu"],
  onlyProfileWithPhoto: ["boolean"],
};

const v1 = fromJson(1, spec);
```

Encode the object/state.

```javascript
const encodedv1 = encode(v1, {
  lookingFor: "bride",
  age: [25, 30],
  religion: "Hindu",
  motherTongue: "Bengali",
  onlyProfileWithPhoto: true,
});
// => 'bHhc9I-aqa'

decode([v1], encodedv1);
// => { lookingFor: 'bride', age: [25, 30], religion: 'Hindu', motherTongue: 'Bengali', onlyProfileWithPhoto: true }
```

Update your spec as your application state space grows. Use versioning
to encode/decode state.

```javascript
const newSpec = {
  ...spec,
  maritialStatus: ["oneOf", "Doesn't Matter", "Never Married", "Divorced", "Widowed", "Awaiting Divorce", "Annulled"],
};

const v2 = fromJson(2, newSpec, (old) => {
  old.maritialStatus = "Doesn't Matter";
  return old;
});

decode([v1, v2], encodedv1);
// => { lookingFor: 'bride', age: [25, 30], religion: 'Hindu', motherTongue: 'Bengali', onlyProfileWithPhoto: true, maritialStatus: "Doesn't Matter" }

const encodedv2 = encode(v2, {
  lookingFor: "bride",
  age: [25, 30],
  religion: "Hindu",
  motherTongue: "Bengali",
  onlyProfileWithPhoto: true,
  maritialStatus: "Never Married",
});
// => 'cHlc9I-aHaa'

decode([v1, v2], encodedv2);
// => { lookingFor: 'bride', age: [25, 30], religion: 'Hindu', motherTongue: 'Bengali', onlyProfileWithPhoto: true, maritialStatus: 'Never Married' }
```

Recursive structure

```javascript
const node = {
  name: ["varchar"],
  children: ["array", ["ref", "node"]],
};

const v1 = fromJson(1, node, (a) => a, { node });
```

## API

### fromJson(version, spec, [migrate], [definitions])

- **version** - spec version number
- **spec** - used to define the structure and domain of the data.

  - **structure**
    * object is defined using `{ key: specForValue, ... }`
    * array is defined using `["array", specForValue]`
    * tuple is defined using `["tuple", specForValueAtIndexZero, specForValueAtIndexOne, ...]`

  - **domain**
    domain is defined using `[domainName, arg1, arg2, ...]`

    | Domain    | Args               | Description                             |
    | --------- | ------------------ | --------------------------------------- |
    | oneOf     | allowed values     | similar to enum; encodes index position |
    | integer   |                    | any integer                             |
    | float     |                    | any float                               |
    | boolean   |                    | true or false                           |
    | fixedchar | size of the string | fixed length string                     |
    | varchar   |                    | variable length string                  |

- **migrate** (optional) - called when decoding older versions. Each
subsequent version’s migrate runs in sequence.

- **definitions** (optional) - object mapping names to specs for
recursive structures. Reference via `["ref", name]`.

### encode(coder, object)

* **coder** - coder created using `fromJson`
* **object** - object to encode

### decode(coders, blob)

* **coders** - array of coders
* **blob** - encoded string returned by `encode`

---
_Source: https://npm.io/package/u-node · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._