what is sparse arrays.

If the array is sparse, the value of the length property is greater than the number of elements.
Ex–
var arr = [undefined × 5, 1, 2, 3];
arr.length;
Ans– 4

Q: In javascript, arrays are sparse.
Ans:yes

Q:In javascript, the length property always tells us how many elements are there in an array.

var arr = [undefined × 5, 1, 2, 3, undefined × 2]

arr.length;
in browser console:
arr = [undefine, undefine, undefine, undefine, undefine, 1,2,3, undefine, undefine];

Ans: no
because length of arr is 10 but element in the array is 3 that is 1,2,3

Q: If an array evaluates to [undefined × 5, 1, 2, 3, undefined × 2], it's length property will have a value of?

Ans: 10
arr = [undefined × 5, 1, 2, 3, undefined × 2];
arr.length;
10

Q: Given an array var x = [20, 30, 40, 50, 60];. If we want the array to be [10, 20, 30, 40, 50, 60, 70], which set of operations should be used?

Ans=> x.unshift(10); x.push(70);

Q: Consider the following code:

var x = [10,20,30,40,50];
x.unshift(60);
x.pop(50);
x.push(70);
The array x now looks like

Ans:–- [60,10,20,30,40,70]