16 lines
462 B
Markdown
16 lines
462 B
Markdown
### isNumber
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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. Because `typeof NaN` is equal to `number`, the `val === val` is for protection. NaN compares unequal (via ==, !=, ===, and !==) to any other value, including to another NaN value.
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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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