56 lines
2.3 KiB
Markdown
56 lines
2.3 KiB
Markdown
---
|
|
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.
|