Add JS Boolean blog

blog_posts/javascript-boolean-function.md

@@ -0,0 +1,54 @@
+---
+title: Where and how can I use the Boolean function in JavaScript?
+type: question
+tags: javascript,function,type
+authors: chalarangelo
+cover: blog_images/javascript-boolean-function.jpg
+excerpt: JavaScript's built-in Boolean function can be very useful for truth-checking data among other things. Learn how to use it and level up your code today.
+---
+
+JavaScript's built-in [`Boolean`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean) is one of those things I find myself suggesting in code reviews quite often as of late, so I thought I could share some tips about it with the world.
+
+**Using Boolean for truth-checking**
+
+The `Boolean()` function is particularly useful when truth-checking data and probably significantly more readable than the double negation (`!!`) operation:
+
+```js
+let x = 'some-value';
+
+// This doesn't look too nice
+if (!!x) {
+  // ...
+}
+
+// This is a lot more readable
+if (Boolean(x)) {
+  // ...
+}
+```
+
+As you can see in the example above, it serves the exact same purpose and is pretty straightforward to use. Similarly, as `Boolean()` is itself a function returning a boolean value, you can use it for truth-checking collections, filtering arrays etc.:
+
+```js
+const values = [0, 0, 2, 0, 3];
+// Use as the callback for Array.prototype.some()
+const hasValidValue = values.some(Boolean);
+// Use as the callback for Array.prototype.filter()
+const nonEmptyValues = values.filter(Boolean);
+```
+
+**Handle Boolean objects with care**
+
+While the `Boolean()` function is pretty useful, you might run into some issues with the `Boolean` object and the `new Boolean()` constructor. The `Boolean` object is an object wrapper for a boolean value, but the tricky part is that, as an object, it's always truthy even if the contained value is `false`!
+
+```js
+let x = new Boolean(false);
+
+if (x) {
+  // This code is executed
+}
+```
+
+For example, the above code will consider `x` truthy, even if it clearly contains `false` as its value. This might some confusing, but you can easily avoid it if you generally avoid using `Boolean` objects and the `new Boolean()` constructor, unless you are entirely certain that you need to use it for some reason. I cannot find any scenarios where I would need to use this, to be honest, so it might not be all that common to begin with.
+
+**Image credit:** [Louis Droege](https://unsplash.com/@lois184?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText) on [Unsplash](https://unsplash.com/s/photos/code?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText)