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

Step 1:
i = 1
arr[1] = arr[0] + arr[2] // arr[1] = 4 + 2 = 6

Step 2:
i = 2
arr[2] = arr[1] + arr[3] // arr[2] = 6 + 5 = 11

alert(arr); // 4, 6, 11, 5

Answer 2

Thank you yaroslav and Vasiliy :)

Answer 3

1). arr[1] = arr[0] + arr[2] = 4 + 2 = 6;
2). arr[2] = arr[1] + arr[3] = 6 + 5 = 11;
arr = [4, 6, 11, 5];
alert(arr);

Answer 4

Better say: "Большое Вам спасибо, Ярослав и Василий!" 😉

Answer 5

Visualize your code execution

(Python, Java, C, C++, JavaScript, Ruby)

https://pythontutor.com

Answer 6

Haha alright. Thank you very much, Yaroslav and Vasily! :)