How To Check If All Values In Array Are False In JavaScript

Checking if all values in an array are false is a common problem in JavaScript programming. Read this article to the end to learn how to check if all values in array are false in JavaScript. Let’s get started.

How to check if all values in array are false in JavaScript

The solution given in this article to check if all values in an array are false in JavaScript is to use the Array.every() method. First, we will learn about every() method, its syntax, and how to use it.

The every() method is used to check all the elements in the input array using a provided callback function. The every() method will return true if all elements pass the test.

Syntax:

every(Callback function)

Parameter:

Callback function: A function is called again for each element. This function performs the element test and returns true if the element passes the test.

If the callback function returns a false value, the every() method will stop checking and return false. If the input array is empty, the every() method will return true.

To check if all the values in the array are false using every() method, we pass this method a callback function that checks if the array element is false.

Example:

// Check if all elements in the array are false
function isFalse(array) {
    return array.every((value) => value === false);
}

// Create an array
const falseArr = [false, false, false, false];
console.log(isFalse(falseArr));

Output:

true

However, this does not work with falsy values other than false because they are not boolean values. There are only six falsy values in JavaScript: false, undefined, null, NaN, 0, and the empty string.

We will use the NOT operator ! to convert the values in the array to boolean values. The NOT operator ! will return true for falsy values. If all values in the array are falsy, the every() method will return true.

Example:

// Check if all elements in the array are false
function isFalse(array) {
    return array.every((value) => !value);
}

// Create an array
const falsyArr = [false, "", 0, null, undefined, NaN];
console.log(isFalse(falsyArr));

Output:

true

Summary

This article shared how to check if all values in array are false in JavaScript. We’ve done this using the every() method. An important note is that testing for false is different from checking for other falsy values like undefined, NaN, etc. To check if an element is falsy, you must use the NOT operator to convert the element’s value to a boolean. Thank you for reading.

Bruce Warren

Hello, my name’s Bruce Warren. You can call me Bruce. I’m interested in programming languages, so I am here to share my knowledge of programming languages with you, especially knowledge of C, C++, Java, JS, PHP.

Name of the university: KMA
Major: ATTT
Programming Languages: C, C++, Java, JS, PHP