Rename articles prefixed with js-

snippets/js/s/double-negation-operator.md

@@ -0,0 +1,37 @@
+---
+title: What does the double negation operator do in JavaScript?
+shortTitle: Double negation operator
+type: question
+language: javascript
+tags: [type]
+author: chalarangelo
+cover: memories-of-pineapple-2
+excerpt: You've probably come across the double negation operator (`!!`) before, but do you know what it does?
+dateModified: 2022-07-26T05:00:00-04:00
+---
+
+JavaScript's negation operator (`!`) is a unary operator, used to invert the truth value of its operand. When used twice, known as the double negation operator (`!!`), it can be used to convert a value to a boolean.
+
+```js
+const x = 1;
+const y = null;
+
+!!x; // true
+!!y; // false
+```
+
+Using the double negation operator is functionally equivalent to using the `Boolean()` function, which we explored in depth in a [previous article](/js/s/boolean-function). In terms of readability and usability, I would still suggest using the `Boolean()` function. It conveys the intent of the operation more clearly, and it's easier to understand at a glance.
+
+```js
+const x = 1;
+const y = null;
+
+Boolean(x); // true
+Boolean(y); // false
+
+const values = [0, 0, 2, 0, 3];
+// Kinda readable, but not great
+values.filter(x => !!x); // [2, 3]
+// Arguably more readable
+values.filter(Boolean); // [2, 3]
+```