# @joookiwi/lazy

> A Javascript implementation based of the Kotlin lazy with reusable fields

Latest version **1.7.3** (published 2026-08-12) · MIT license · 0 weekly downloads

## Install

```sh
npm install @joookiwi/lazy
pnpm add @joookiwi/lazy
yarn add @joookiwi/lazy
bun add @joookiwi/lazy
```

## Health

**Score 70/100 (B)** — status: active.

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

Warnings: low downloads.

## Facts

| | |
|---|---|
| Version | 1.7.3 |
| Published | 2026-08-12 |
| First published | 2023-06-28 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Dependencies | 1 |
| Unpacked size | 124.6 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 1 |
| Author | JóôòKiwi |
| Maintainers | joookiwi |
| Keywords | lazy, kotlin lazy, lazy pattern, object holder |

## Links

- npm: https://www.npmjs.com/package/@joookiwi/lazy
- Repository: https://github.com/joooKiwi/lazy
- Homepage: https://github.com/joooKiwi/lazy#readme
- Issues: https://github.com/joooKiwi/lazy/issues
- Funding: https://github.com/sponsors/joooKiwi
- npm.io page: https://npm.io/package/@joookiwi/lazy

## Dependencies (1)

- [@joookiwi/type](https://npm.io/package/@joookiwi/type.md) ^1.2.2

## Recent versions

- 1.7.3 (latest) — 2026-08-12
- 1.7.2 — 2026-02-24
- 1.7.1 — 2025-08-12
- 1.7.0 — 2025-01-09
- 1.6.0 — 2024-11-08
- 1.5.0 — 2024-07-21
- 1.4.0 — 2024-04-01
- 1.3.0 — 2024-02-19
- 1.2.1 — 2023-12-04
- 1.2.0 — 2023-09-28
- 1.1.1 — 2023-08-14
- 1.1.0 — 2023-08-14
- 1.0.1 — 2023-07-02
- 1.0.0 — 2023-06-28
- 0.3.0 — 2023-06-28

## README

# Lazy (javascript version)

## Table of content
* [Installation](#installation)
* [Usage](#usage)
  * [Lazy value](#lazy-value)
  * [Non-lazy value](#non-lazy-value)
  * [Specialized non-lazy value](#specialized-non-lazy-value)
  * [Common lazy](#common-lazy)
* [Contribution](#contribution)

This project is an implementation based on the [Kotlin Lazy](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-lazy/).
All of this with additional features to help the reusing of some values.

## Installation
```
npm install @joookiwi/lazy
npm i @joookiwi/lazy

npm install --save @joookiwi/lazy
npm i -S @joookiwi/lazy

npm install --save-dev @joookiwi/lazy
npm i -D @joookiwi/lazy
```

## Usage
The usage is similar to the kotlin usage like `val value by lazy { someValue }` in kotlin
as well as the non-lazy implementation like `val value = lazyOf(someValue)`.

But since there is no significant dependency toward this specifically.
Here is an implementation of the lazy via 2 functions
 - `lazy` to load the value later
 - `lazyOf` to have a `Lazy` but with an already loaded value

### Lazy value

Using the lazy value will always return a `Lazy` object holding a value.

```javascript
import {lazy} from "@joookiwi/lazy"

const firstValue = lazy(() => 2)
firstValue.isInitialized // false
firstValue.value         // 2
firstValue.isInitialized // true
```

### Non-lazy value

If the value is already known, then just use `lazyOf()` in order to have a `Lazy` with an already loaded value.

```javascript
import {lazyOf} from "@joookiwi/lazy"

const firstValue = lazyOf(2)
firstValue.isInitialized // true
firstValue.value         // 2
firstValue.isInitialized // true
```

### Specialized non-lazy value

There are some specialized `lazyOf()`-like `Lazy` to reuse the `CommonLazy` values depending on what it has received:
 - `booleanLazyOf` for the `boolean`
 - `numberLazyOf` for the `number`
 - `bigintLazyOf` for the `bigint`
 - `dateLazyOf` for the `Date`

### Common lazy

When using the lazy methods,
it always creates a new instance.

But, there could be some cases where an already known value is there.

Here is the full list of the common `Lazy` instances:

| Value                                             | With string | With character | With BigInt |
|---------------------------------------------------|:------------|:---------------|:------------|
| `null`                                            | yes         |                |             |
| `undefined`                                       | yes         |                |             |
| `true` / `false`                                  | yes         |                |             |
| `-1` / `0` / `1` / `2`                            | yes         | yes            | yes         |
| `NaN` / `∞` (infinity) / `-∞` _(-infinity)_       | yes         |                |             |
| `ln(2)` / `ln(10)`                                |             |                |             |
| `log₂(E)` / `log₁₀(E)`                            |             |                |             |
| `E`, `π` _(pi)_, `τ` _(tau)_                      |             |                |             |
| ` ` / `\t` / `\n`                                 |             | yes            |             |
| epoch date                                        |             |                |             |
| invalid date                                      | yes         |                |             |
| empty String → `''`                               |             |                |             |
| empty object → `Readonly<{}>`                     |             |                |             |
| empty Array → `readonly []`                       |             |                |             |
| empty Set → `ReadonlySet<never>`                  |             |                |             |
| empty WeakSet → `Readonly<WeakSet<never>>`        |             |                |             |
| empty Map → `ReadonlyMap<never, never>`           |             |                |             |
| empty WeakMap → `Readonly<WeakMap<never, never>>` |             |                |             |

## Contribution
You can contribute to great simple packages.
All with similar behaviour across different languages (like Java, Kotlin, C# and PHP).
It can be done 2 different ways:
- [GitHub sponsor](https://github.com/sponsors/joooKiwi) or
- [!["Buy me a Coffee"](https://img.buymeacoffee.com/button-api/?&button_colour=40DCA5&font_colour=ffffff&font_family=Cookie&outline_colour=000000&coffee_colour=FFDD00)](https://www.buymeacoffee.com/joookiwi)

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