30 lines
782 B
Markdown
30 lines
782 B
Markdown
---
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title: Value is promise-like
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tags: type,function,promise
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expertise: intermediate
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cover: blog_images/digital-nomad-13.jpg
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firstSeen: 2017-12-31T14:25:43+02:00
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lastUpdated: 2020-10-20T23:02:01+03:00
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---
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Checks if an object looks like a [`Promise`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise).
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- Check if the object is not `null`, its `typeof` matches either `object` or `function` and if it has a `.then` property, which is also a `function`.
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```js
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const isPromiseLike = obj =>
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obj !== null &&
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(typeof obj === 'object' || typeof obj === 'function') &&
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typeof obj.then === 'function';
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```
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```js
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isPromiseLike({
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then: function() {
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return '';
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}
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}); // true
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isPromiseLike(null); // false
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isPromiseLike({}); // false
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```
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