# EventHandler.isEventHandler

Checks if a value is an `EventHandler`.

## Signatures

```ts
export declare function isEventHandler<Ev extends Event, E = never, R = never>(handler: unknown): handler is EventHandler<Ev, E, R>;
```

## Why

The nominal key distinguishes handler descriptions from arbitrary functions
before template compilation.

## Ownership and lifetime

The guard only inspects the value and acquires nothing.

## Examples

```ts
import * as EventHandler from "@typed/template/EventHandler"

const handler = EventHandler.make((event) => console.log("Click"))
const isHandler = EventHandler.isEventHandler(handler)
console.log(isHandler) // true

const notHandler = (event: Event) => console.log("Click")
const isNotHandler = EventHandler.isEventHandler(notHandler)
console.log(isNotHandler) // false
```