JavaScript: Why does arr length is 42?

Question

var a = [];
a[0] = 0;
a.push(1);
a[41] = 41;
console.log(a.length); //42

// console.log(a) outputs only three elements: [0,1,41]

How does js count array length?

Answer 1

it start from index 0. so count the 0 too

Answer 2

Because index start from 0 and last index is 41 that's why length is 42.