Trying to find the sum of the array elements (with the value entered from the screen). Why am I getting NaN?

Question

JavaScript

var 	mas=[];
    sum=0;
  for (var i =1; i < 4; i++) {
    mas.push(prompt("element №" + i));
    sum = sum + parseInt(mas[i]);
    alert(mas);
    alert(sum);
  }

Answer 1

Arrays have an index starting at 0.
For debugging, use console.log instead of alert. It is more comfortable.