Tipify number validation

content/languages/javascript.yaml

@@ -364,6 +364,8 @@ references:
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/trunc
  Number: >-
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number
+ Number(): >-
+ https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/Number
  Number.EPSILON: >-
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/EPSILON
  Number.MAX_SAFE_INTEGER: >-

content/redirects.yaml

@@ -2920,3 +2920,6 @@
 - from: /js/s/count-substrings
  to: /js/s/count-occurences
  status: 301!
+- from: /js/s/validate-number
+ to: /js/s/number-validation
+ status: 301!

content/snippets/js/s/number-validation.md

@@ -0,0 +1,26 @@
+---
+title: Validate a number in JavaScript
+shortTitle: Validate number
+type: tip
+language: javascript
+tags: [math]
+cover: flower-portrait-9
+excerpt: Check if a value can be safely converted to a number in JavaScript.
+dateModified: 2024-05-17
+---
+
+Number validation is probably one of the hardest things to do even for intermediate developers. However, it's a necessary evil, especially when working with **user input**. It's even more so in JavaScript, due to the language's quirks and the fact that it's loosely typed.
+
+While, a simple check that `parseFloat()` produces a sensible **numeric value** might seem enough, it's a little more involved than that. You also need to check for `NaN`, using `Number.isNaN()`, and for `Infinity`, using `Number.isFinite()`.
+
+And, as if that wasn't already enough, you also need to check if the **coercion** of the value to a number is correct, using `Number()` and the loose equality operator (`==`). Putting everything together, you get a pretty robust number validation function.
+
+```js
+const validateNumber = n => {
+ const num = parseFloat(n);
+ return !Number.isNaN(num) && Number.isFinite(num) && Number(n) == n;
+}
+
+validateNumber('10'); // true
+validateNumber('a'); // false
+```