Tipify copy-sign-to-number

content/snippets/js/s/copy-sign-to-number.md

@@ -1,16 +1,21 @@
 ---
-title: Copy sign to number
-type: snippet
+title: Copy sign from one number to another in JavaScript
+shortTitle: Copy sign to number
+type: tip
 language: javascript
 tags: [math]
 cover: cloudy-mountaintop
-dateModified: 2020-10-07
+excerpt: Copy the sign of one number to another without changing its absolute value.
+dateModified: 2024-05-28
 ---
 
-Returns the absolute value of the first number, but the sign of the second.
+If you've ever worked extensively with numeric values, you might have stumbled upon a case where you need to **change the sign of a number**. This is relatively simple, but what if you want to **copy the sign** from another value. Naively, most of us would simply add a ternary operator and check if the second number is positive or negative, then do the same for the first number. But there's a much simpler way to do this.
 
-- Use `Math.sign()` to check if the two numbers have the same sign.
-- Return `x` if they do, `-x` otherwise.
+In the simplest terms possible, either the target value has the correct sign (same as the source value) or it doesn't. All you really need to **compare are the signs** of the two numbers. If they're the same, you're done. If they're different, you just need to change the sign of the target value.
+
+So how can that be done? Luckily, `Math.sign()` can help us out here. This methods returns either `1` (positive), `0` (zero), or `-1` (negative) depending on the sign of the number. By comparing the signs of the two numbers, we can easily determine if the sign needs to be changed.
+
+The only thing left to do is use the ternary operator (`?`) to conditionally apply the unary `-` operator to the target value. If the signs are the same, the target value remains unchanged. If they're different, the **sign is flipped**.
 
 ```js
 const copySign = (x, y) => Math.sign(x) === Math.sign(y) ? x : -x;