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snippets/js/s/validate-number.md

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+---
+title: Validate number
+type: snippet
+language: javascript
+tags: [math]
+cover: flower-portrait-9
+dateModified: 2020-10-22T20:23:26+03:00
+---
+
+Checks if the given value is a number.
+
+- Use `parseFloat()` to try to convert `n` to a number.
+- Use `Number.isNaN()` and logical not (`!`) operator to check if `num` is a number.
+- Use `Number.isFinite()` to check if `num` is finite.
+- Use `Number` and the loose equality operator (`==`) to check if the coercion holds.
+
+```js
+const validateNumber = n => {
+  const num = parseFloat(n);
+  return !Number.isNaN(num) && Number.isFinite(num) && Number(n) == n;
+}
+```
+
+```js
+validateNumber('10'); // true
+validateNumber('a'); // false
+```