Can someone pls explain why this code is outputting 4, 6, 11, 5 ?

Question

var arr = [4, 3, 2, 5];
for(var i = 1; i < 3; i++) {
arr[i] = arr[i-1] + arr[i + 1];
}
alert(arr);

Answer 1

arr[i] = arr[i-1] + arr[i + 1];

i=1
arr[1] = arr[0] + arr[2] = 4 + 2 = 6 ;

I=2
arr[2] = arr[1] + are[3] = 6+5=11;

I=3<3 false, loop exits

arr = [ 4, 6,11,5 ] ;
Only 2 values changing..
hope it helps.....

Answer 2

Yes it helped, i think i understand it now :)