---
title: Transformer
url: https://www.fastly.com/documentation/reference/compute/sdks/javascript/js-compute/globals/interface.Transformer/
---

**Kind:** Interface  
**Module:** [globals](https://www.fastly.com/documentation/reference/compute/sdks/javascript/js-compute/globals/)  
**Package:** @fastly/js-compute 4.0.1  
**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L2030

```javascript
interface Transformer<I = any, O = any>
```

## Properties

### flush

**Type:** `TransformerFlushCallback<O>`  
**Flags:** optional  
**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L2031

### readableType

**Type:** `undefined`  
**Flags:** optional  
**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L2032

### start

**Type:** `TransformerStartCallback<O>`  
**Flags:** optional  
**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L2033

### transform

**Type:** `TransformerTransformCallback<I, O>`  
**Flags:** optional  
**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L2034

### writableType

**Type:** `undefined`  
**Flags:** optional  
**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L2035