How to Check if All Values in Array Are True in JavaScript

In today’s post, we’ll learn how to check if all values in an array are true or not in JavaScript.

Use the every() Method to Check if All Values in Array Are True in JavaScript

The every() method is a built-in method provided by JavaScript that examines whether all elements inside the array pass the condition/criteria carried out through the provided function. Based on the function, it returns either a true or false boolean value.

Syntax:

every((element, index) => {/* Logic goes here */})

The first parameter is the current element processed in the array. The index parameter is the current element’s index processed in the array.

The every() method no longer mutates the array on which it’s referred to as. Calling the every() method on an empty array will return true for any condition.

This method returns true if the callbackFn function returns a truthy value for every array element; otherwise, it returns false. The falsy values in JavaScript are false, undefined, null, 0, NaN (Not a Number) and empty string.

For each element present in the array, the every() method runs the provided callbackFn function once until one falsy/incorrect value is found. If such an element is found, the every() method returns false immediately, and the remaining elements are skipped.

If callbackFn returns true for all elements present in an array, they all return true. callbackFn is only called for array indexes that have values ​​assigned.

It is not called for dropped indexes or has not been assigned values.

You can get more information about the every() method in the documentation for every.

Let’s understand it with the following example:

const inputArray = [true, true, true, true, true, false, true, true, true];
console.log(inputArray.every(x => x === true));

We have defined an input array with 8 true values and one false value within the above example. When the every() method encounters a false value on the fifth index, it will stop the execution and return false.

Attempt to run the above code snippet in any browser that supports JavaScript; it will display the result below.

Output:

false

Access the demo here.