23 lines
552 B
Markdown
23 lines
552 B
Markdown
---
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title: Value is number
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tags: type,math
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cover: red-petals
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firstSeen: 2017-12-17T17:55:51+02:00
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lastUpdated: 2020-09-15T16:28:04+03:00
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---
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Checks if the given argument is a number.
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- Use `typeof` to check if a value is classified as a number primitive.
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- To safeguard against `NaN`, check if `val === val` (as `NaN` has a `typeof` equal to `number` and is the only value not equal to itself).
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```js
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const isNumber = val => typeof val === 'number' && val === val;
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```
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```js
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isNumber(1); // true
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isNumber('1'); // false
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isNumber(NaN); // false
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```
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