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snippets/articles/s/javascript-boolean-function.md

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+---
+title: Where and how can I use the Boolean function in JavaScript?
+shortTitle: Boolean function use-cases
+type: question
+language: javascript
+tags: [function,type]
+author: chalarangelo
+cover: rocky-lake
+excerpt: JavaScript's Boolean function can be used for truth-checking data among other things. Learn how to use it and level up your code today.
+dateModified: 2021-06-12T19:30:41+03:00
+---
+
+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 `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 `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.