[tsigel]

var arr = [1,2,null,3,,4,5];
var summ = 0;
function s(x){
  var sum = 0;
  summ += x * x;  
  return sum += x*x;
}; 
for(var keys = 0;keys<arr.length;keys++){
    if(!arr[keys]) continue;
    var xx = arr[keys];    
    alert('Summa = ' + s(xx));
  };
alert('Summa elementov massiva = ' + summ);