JavaScript Booleans

JavaScript has a Boolean data type that can have two values: true or false.

A Boolean value is often used in conditional statements to check if a certain condition is true or false.

For example, you might use a Boolean value to check if a user is logged in or not, or to check if an input is valid or not.

Here is a basic example:

Boolean(10 > 5) // the output will be true
Boolean(10 < 5) // the output will be false
Boolean(10 == 5) // the output will be false

The Boolean() Function

The Boolean() function is a built-in JavaScript function that can be used to convert a value to a Boolean.

It returns a Boolean value of true if the value passed to it is truthy, and false if the value passed to it is falsy.

Here are some examples of how to use the Boolean() function:

Boolean(true) // returns true
Boolean(false) // returns false
Boolean(1) // returns true
Boolean(0) // returns false
Boolean("hello") // returns true
Boolean("") // returns false
Boolean(undefined) // returns false
Boolean(null) // returns false

In practice, this function is not needed that much, as JavaScript will automatically convert a value to a Boolean in many situations, such as when it's used in a conditional statement or as the operand of logical operators.

if (value) // this will be true if the value is truthy
var x = value && otherValue // this will be true if both value and otherValue are truthy

Boolean Properties

Boolean properties are properties of an object that have a Boolean value, that is, either true or false. They are used to represent a certain state or attribute of the object.

For example, a visible property of a UI element could be a Boolean property that indicates whether the element is currently visible on the screen or not.

A checked property of a checkbox input could be a Boolean property that indicates whether the checkbox is currently checked or not.

In JavaScript, you can access and set the value of a Boolean property using the dot notation . or the square bracket notation [ ].

For example, if an object called element has a visible property, you can access its value using the following code:

let isVisible = element.visible;

You can also set its value using the following code:

element.visible = false;

Another example,

let checkbox = document.getElementById("myCheckbox");
console.log(checkbox.checked); // Output: false
checkbox.checked = true;
console.log(checkbox.checked); // Output: true

Boolean properties are widely used in JavaScript frameworks such as React, Angular and Vue.js to handle the state of a component or element, and to determine when to re-render or update the component based on the changes in state.

Boolean Methods

Boolean methods are methods that are associated with the Boolean object in JavaScript and are used to perform specific operations or calculations on Boolean values.

For example, the toString() method is a Boolean method that can be used to convert a Boolean value to a string.

let myBoolean = true;
console.log(myBoolean.toString()); // Output: "true"

Another example, the valueOf() method is a Boolean method that can be used to return the primitive value of a Boolean object.

let myBoolean = true;
console.log(myBoolean.valueOf()); // Output: true

There are not many built-in boolean methods, but developers sometimes use them to create utility functions for handling boolean values more easily.

For example, you can create a method called toggle() that changes the value of a Boolean variable from true to false or vice versa.

let myBoolean = true;

function toggle(value) {
  return !value;
}
console.log(toggle(myBoolean)); // Output: false

In JavaScript frameworks such as React, Angular and Vue.js, the concept of Boolean methods usually refers to methods that are associated with the component or element and are used to handle the state and behavior of the component.

JS Basics