# computed-value

> Computed values in reactive style of programming

Latest version **0.1.3** (published 2013-03-11) · MIT license · 0 weekly downloads

## Install

```sh
npm install computed-value
pnpm add computed-value
yarn add computed-value
bun add computed-value
```

## Health

**Score 15/100 (F)** — status: abandoned.

Positive: no vulnerabilities.

Warnings: low downloads; no types; no esm support; pre 1.0.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 0.1.3 |
| Published | 2013-03-11 |
| First published | 2013-03-09 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | none |
| Module format | CommonJS |
| Node | >=0.9.12 |
| Dependencies | 1 |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 3 |
| Author | Tristan Slominski |
| Maintainers | tristanls |
| Keywords | reactive, computed, property, value |

## Links

- npm: https://www.npmjs.com/package/computed-value
- Repository: git@github.com:tristanls/node-computed-value
- npm.io page: https://npm.io/package/computed-value

## Dependencies (1)

- [computed-value-stream](https://npm.io/package/computed-value-stream.md) 0.1.0

## Recent versions

- 0.1.3 (latest) — 2013-03-11
- 0.1.2 — 2013-03-09
- 0.1.1 — 2013-03-09
- 0.1.0 — 2013-03-09

## README

# computed-value

    Stability: 1 - Experimental

_Stability as defined by [Node.js](http://nodejs.org/api/documentation.html#documentation_stability_index)_

A module for creating computed value in reactive programming style. 

## Installation

    npm install computed-value

## Usage

Below example can be also found in [examples/fullname.js](examples/fullname.js).

```javascript
var computedValue = require('computed-value');

var first = computedValue('Tom');
var last = computedValue('Dale');
var fullName = computedValue(first, last, function(first, last) {
  return first + ' ' + last;
});

console.log(fullName.value);

first.write('Bob');
console.log(fullName.value);

fullName.on('update', function(updatedValue) {
  console.log('update:', updatedValue);
});

last.write('Johnson');
```

The output of running the above script will be:

    Tom Dale
    Bob Dale
    update: Bob Johnson

## computedValue()

If no arguments are passed to the function, it simply returns the computed value stream. You can read it's `value` (it will be `undefined`), and you can `write` to it to initialize it.

```javascript
var computedValue = require('computed-value');

var name = computedValue();
console.log(name.value);
// -> undefined

name.write('Julia');
console.log(name.value);
// -> 'Julia'
```

## computedValue(initialValue)

If a single, non-function argument is passed, `computedValue` will initialize the underlying computed value stream with the `initialValue`, then return it.

```javascript
var computedValue = require('computed-value');

var name = computedValue('Julia');
console.log(name.value);
// -> 'Julia'

name.write('Julie');
console.log(name.value);
// -> 'Julie'
```

## computedValue(dependency[, dependency...], calculationFunction)

If more than one arguments are passed in, `computedValue` assumes that the last argument is a function that will take as input the values of each `dependency` listed before it, just like in the `Usage` example above. Each `dependency` must be a computed value itself in order for the mechanism to work correctly. (it will attempt to lookup `value` property as well as try to register a listener for an `update` event, see [index.js](index.js) for details).

```javascript
var computedValue = require('computed-value');

var first = computedValue('Tom');
var last = computedValue('Anderson');
var fullName = computedValue(first, last, function(first, last) {
  return first + ' ' + last;
});

console.log(fullName.value);
// -> 'Tom Anderson'

var title = computedValue('Mr.');
var titledFullName = computedValue(title, fullName, function(title, fullName) {
  return title + ' ' + fullName;
});

console.log(titledFullName.value);
// -> 'Mr. Tom Anderson'

first.write('Jake');
console.log(titledFullName.value);
// -> 'Mr. Jake Anderson'
```

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