---
title: "@unikvs/passthrough"
description: "Explains how to use @unikvs/passthrough, which passes data through without transforming it."
---

## Overview [#overview]

`@unikvs/passthrough` is a Transformer plugin that passes input through without transforming it. Transformer

`encode` and `decode` return the data they receive, and `getEncodable` and `getDecodable` return streams that pass chunks through. They affect neither the contents of the data nor the chunk boundaries.

This transformer is always open. No explicit `open` or `close` is needed; `isOpen` always returns `true` and `name` is always `"PassThrough"`.

Install it as follows.

```package-install
npm install @unikvs/passthrough
```

## Usage [#usage]

Register it with `appendTransformer`. It adds a no-op pipeline to the storages registered after it.

```ts
import { PassThrough } from "@unikvs/passthrough";
import { Memory } from "@unikvs/memory";
import { UniKvs, type PlainValue } from "unikvs";

const kvs = UniKvs.config<{ greeting: PlainValue<string> }>()
  .appendTransformer(new PassThrough())
  .appendStorage(new Memory())
  .create();

await kvs.open();

await kvs.set("greeting", "hello");
const greeting = await kvs.get("greeting");

await kvs.close();
```

## Streams [#streams]

`getEncodable` and `getDecodable` return a TransformStream that emits its input unchanged. Neither the chunk boundaries nor the references change. An empty stream completes empty.

## Use Cases [#use-cases]

Use it to turn a transformer on or off with conditional branching. To turn it off, replace it with `PassThrough` instead of removing it from its position. You can switch a transformation on and off based on the environment or configuration without changing the pipeline structure.

```ts
import { Compression } from "@unikvs/compression";
import { PassThrough } from "@unikvs/passthrough";
import { Memory } from "@unikvs/memory";
import { UniKvs, type Value } from "unikvs";

// Assumed to come from configuration or an environment variable.
const enableCompression = true;
const transformer = enableCompression ? new Compression("gzip") : new PassThrough();

const kvs = UniKvs.config<{ data: Value<Uint8Array<ArrayBuffer>> }>()
  .appendTransformer(transformer)
  .appendStorage(new Memory())
  .create();

await kvs.open();

await kvs.set("data", Uint8Array.from([0, 1, 2]));
const data = await kvs.get("data");

await kvs.close();
```

`Compression` and `PassThrough` both implement `ITransformer`, so you can swap them at the same position.

## Notes [#notes]

- Because it does not transform data, using it alone does not change stored values.
- To log reads and writes, use `@unikvs/debug` instead. `@unikvs/passthrough` neither logs data nor reads variables.