> For the complete documentation index, see [llms.txt](https://docs.corets.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.corets.io/observables/value.md).

# Value

Source code is hosted on [GitHub](https://github.com/corets/value)

{% tabs %}
{% tab title="yarn" %}

```bash
yarn add @corets/value
```

{% endtab %}

{% tab title="npm" %}

```bash
npm install --save @corets/value
```

{% endtab %}
{% endtabs %}

Seamless React integration is shipped in a separate package:

{% content-ref url="/pages/-MeeCjonF5MnSCR9TohM" %}
[useValue](/hooks/use-value.md)
{% endcontent-ref %}

These packages provide extended functionality and are built on top of this library:

{% content-ref url="/pages/-MeeBQ0F094TDCsvnMbA" %}
[Store](/observables/store.md)
{% endcontent-ref %}

{% content-ref url="/pages/-MeeBIuqvkAwUjx0ORFs" %}
[List](/observables/list.md)
{% endcontent-ref %}

{% content-ref url="/pages/-MeeEDpap1iIyRi7d5Py" %}
[Local Storage Value](/observables/local-storage-value.md)
{% endcontent-ref %}

{% content-ref url="/pages/-MeeEM7lap525qmHR0yU" %}
[Local Storage Store](/observables/local-storage-store.md)
{% endcontent-ref %}

{% content-ref url="/pages/-MeeEJek1b6Kf63VvtQ5" %}
[Local Storage List](/observables/local-storage-list.md)
{% endcontent-ref %}

## createValue()

Create a new observable value:

```typescript
import { createValue } from "@corets/value"

const count = createValue(0)
```

Create a new observable value without the factory function:

```typescript
import { Value } from "@corets/value"

const value = new Value(0)
```

Create a new observable value with a custom differ:

```typescript
import { createValue } from "@corets/value"

const differ = (oldValue, newValue) => true
const count = createValue(0, { differ })
```

## Value.get()

Get current value:

```typescript
value.get()
```

## Value.set()

Update current value:

```typescript
value.set("new value")
```

## Value.listen()

Listen to value changes:

```typescript
const unsubscribe = value.listen((value) => console.log(value))

unsubscribe()
```

Invoke listener immediately:

```typescript
value.listen((value) => console.log(value), { immediate: true })
```

Listen with a custom differ:

```typescript
const differ = (oldValue, newValue) => true

value.listen((value) => console.log(value), { differ })
```

## Value.use()

Convenience method for people used to React's `useState` syntax:

```typescript
import { createValue } from "@corets/value"

const [value, setValue] = createValue(1).use()
```