---
title: WritableStreamDefaultWriter
summary: This Streams API interface is the object returned by WritableStream.getWriter() and once created locks the < writer to the WritableStream ensuring that no other streams can write to the underlying sink.
url: https://www.fastly.com/documentation/reference/compute/sdks/javascript/js-compute/globals/interface.WritableStreamDefaultWriter/
---

**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#L1967

```javascript
interface WritableStreamDefaultWriter<W = any>
```

This Streams API interface is the object returned by WritableStream.getWriter() and once created locks the < writer to the WritableStream ensuring that no other streams can write to the underlying sink.

## Constructor

**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L1982

```javascript
new WritableStreamDefaultWriter(stream: WritableStream<W>)
```

**Parameters**

- `stream`: `WritableStream<W>`

## Properties

### closed

**Type:** `Promise<undefined>`  
**Flags:** read-only  
**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L1968

### desiredSize

**Type:** `number | null`  
**Flags:** read-only  
**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L1969

### ready

**Type:** `Promise<undefined>`  
**Flags:** read-only  
**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L1970

## Methods

### abort

**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L1971

```javascript
abort(reason?: any): Promise<void>
```

**Parameters**

- `reason`: `any` (optional)

**Returns**

`Promise<void>`

### close

**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L1972

```javascript
close(): Promise<void>
```

**Returns**

`Promise<void>`

### releaseLock

**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L1973

```javascript
releaseLock(): void
```

**Returns**

`void`

### write

**Source:** https://github.com/fastly/js-compute-runtime/blob/70cf30af4e657879b2d1e7eafab880e39e3a3f7d/types/globals.d.ts#L1974

```javascript
write(chunk: W): Promise<void>
```

**Parameters**

- `chunk`: `W`

**Returns**

`Promise<void>`