How to initialize a boolean array in JavaScript ?

A Boolean array is a collection of variables that can hold only two values: true or false. In JavaScript, Boolean values represent the simplest forms of truthiness and are essential for controlling flow in your programs, such as in conditional statements and loops.

Why Use Boolean Arrays?

Boolean arrays are useful when you need to track binary states, like whether certain conditions are met or whether elements in a collection are active/inactive.

Boolean arrays in JavaScript can be initialized using the methods:

Approach 1: Using Simple for loop

To initialize a Boolean array we can use a Simple for loop to iterate over the array and add Boolean values to it.

Syntax:

// boolean array initialization using for loop
let arr_name = [];
for(initialize variable; condition; increment/decrement){
    arr_name.push(false/true);
}

Example: In this example, we will use a simple for loop.

let arr1 = [];
for (let i = 0; i < 5; i += 1) {
    arr1.push(true);
}
console.log(arr1);

[ true, true, true, true, true ]

Approach 2: Using fill() method

We can also use a fill() method. To use the fill() method we use the `Array()` constructor in JavaScript and create a new array of some given length and then use the inbuilt fill() method in JavaScript to initialize a Boolean array.

Syntax:

// boolean array initialization using fill() method
let arr_name = new Array(arr_length).fill(false/true);

Example: In this example, we will use fill() method.

let arr1 = new Array(5).fill(true);
console.log(arr1); 

[ true, true, true, true, true ]

Approach 3: Using from() method

The third method we can use to initialize a Boolean array is the from() method from JavaScript. To use this method we use the `Array` constructor and then call from the () method from it. In from() method we have to pass parameters length and (Val, index) which points towards the value(true/false).

Syntax:

// boolean array initialization using from() method
let arr_name = Array.from(
    {length}, (val,index) => false/true);

Example: In this example, we will use from() method.

let arr1 = Array.from({ length: 5 }, (val, index) => false);
console.log(arr1);

[ false, false, false, false, false ]

Approach 4: Using map() method

In this method use first initialize the Array constructor with the spread operator and then use the map() method to initialize the Boolean Array in JavaScript.

Syntax:

// boolean array initialization using map() method
const array_name = [...Array(length)].map(() => {
    return false/true;
});

Example: In this example, we will use map() method.

const arr1 = [...Array(5)].map(() => {
    return false;
});
console.log(arr1);

[ false, false, false, false, false ]