---
url: /mosaic/api/core/param.md
---
# Param

A `Param` is a reactive variable for an individual value.

## isParam

`isParam(value)`

Returns `true` if the input value is a `Param`, false otherwise.

## Param.value

`Param.value(value)`

Create a new Param with the given initial *value*.

## Param.array

`Param.array(values)`

Create a new Param over an array of initial *values*, which may contain nested Params.

## value

`param.value`

Retrieves the current value of a Param instance.

## update

`param.update(value, options)`

Update the Param with a new *value*.
The *options* object may include a *force* flag indicating if the Param
should emit a 'value' event even if the internal value is unchanged.

## addEventListener

`param.addEventListener(type, callback)`

Add an event listener *callback* function for the specified event *type*.
Params support `"value"` type events only.

## removeEventListener

`param.removeEventListener(type, callback)`

Remove an event listener *callback* function for the specified event *type*.