26 lines
639 B
Markdown
26 lines
639 B
Markdown
---
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title: validateNumber
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tags: math,intermediate
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firstSeen: 2017-12-17T17:55:51+02:00
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lastUpdated: 2020-10-22T20:23:26+03:00
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---
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Checks if the given value is a number.
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- Use `parseFloat()` to try to convert `n` to a number.
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- Use `!Number.isNaN()` to check if `num` is a number.
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- Use `Number.isFinite()` to check if `num` is finite.
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- Use `Number()` and the loose equality operator (`==`) to check if the coercion holds.
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```js
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const validateNumber = n => {
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const num = parseFloat(n);
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return !Number.isNaN(num) && Number.isFinite(num) && Number(n) == n;
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}
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```
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```js
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validateNumber('10'); // true
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validateNumber('a'); // false
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```
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