# what does this operation tell if(!arr.some(isNaN)) JavaScript

## What does this operation tell if(!arr.some(isNaN)) JavaScript?

This operation is checking if all the elements in the array are numbers or not using the isNaN function in JavaScript. The isNaN function returns true if the value is not a number, and false if it is a number.

### Explanation:

The expression arr.some(isNaN) will return true if any of the elements in the array is not a number. The some() method tests whether at least one element in the array passes the test implemented by the provided function. In this case, the function being called is isNaN.

The if(!arr.some(isNaN)) statement checks whether the some() method returns false. This means that all the elements in the array are numbers and not NaN.

### Example:

const arr = [1, 2, 3, 4, 5];
const isAllNumbers = !arr.some(isNaN);

console.log(isAllNumbers); // true

In this example, an array of numbers is created and assigned to the variable arr. The isAllNumbers variable is assigned the value of true, since all the elements in the array are numbers.

### Alternative ways:

An alternative way to check if an array contains only numbers is to use the every() method. The every() method tests whether all elements in the array pass the test implemented by the provided function. In this case, the function being called is isFinite, which will return true for numbers and false for NaN and Infinity.

const arr = [1, 2, 3, 4, 5];
const isAllNumbers = arr.every(isFinite);

console.log(isAllNumbers); // true

In this example, the isAllNumbers variable is assigned the value of true, since all the elements in the array are numbers.