# Composite.updateTypeaheadBuffer

Appends within the timeout window and starts a new query after the buffer expires.

## Signatures

```ts
export declare function updateTypeaheadBuffer(buffer: TypeaheadBuffer, key: string, now: number, timeout?: number): TypeaheadBuffer;
```

## Why

Separating this deterministic policy from event wiring lets applications test it directly and
reuse it in custom composites.

## Ownership and lifetime

This is a synchronous calculation. It acquires no resources and does not mutate the input array,
state, event, or DOM.

## Examples

```ts
import * as Composite from "@typed/ui/Composite";

const buffer = Composite.updateTypeaheadBuffer({ value: "a", updatedAt: 100 }, "b", 200);
```