26 lines
807 B
Markdown
26 lines
807 B
Markdown
---
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title: isDuplexStream
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tags: node,type,intermediate
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---
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Checks if the given argument is a duplex (readable and writable) stream.
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- Check if the value is different from `null`, use `typeof` to check if a value is of type `object` and the `pipe` property is of type `function`.
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- Additionally check if the `typeof` the `_read`, `_write` and `_readableState`, `_writableState` properties are `function` and `object` respectively.
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```js
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const isDuplexStream = val =>
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val !== null &&
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typeof val === 'object' &&
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typeof val.pipe === 'function' &&
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typeof val._read === 'function' &&
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typeof val._readableState === 'object' &&
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typeof val._write === 'function' &&
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typeof val._writableState === 'object';
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```
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```js
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const Stream = require('stream');
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isDuplexStream(new Stream.Duplex()); // true
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```
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