findindex3.js

let num = new Array(3); // creating an empty array with length 3

console.log(num); // [empty × 3]

console.log(num[0]); // undefined 

// the callback function passed to Array.some method will not check the callback for unassigned values 

num.some(a => {console.log(a); return a === undefined }) // false

// But Array.findIndex will check the callback function for unassigned values also  

num.findIndex(a => {console.log(a); return a === undefined }) // undefined will be printed -   0 will be returned