```
var addTwoNumbers = function(l1, l2) {
var arr = [],
carry = 0,
len1 = l1.length,
len2 = l2.length,
len = Math.max(len1,len2);
for (var i=0; i<len; i++){
var sum = (l1[i]||0) + (l2[i]||0) + carry;
if (sum >= 10){
carry = 1;
sum -= 10;
} else {
carry = 0;
}
arr.push(sum);
if (i == len-1 && carry == 1){
arr.push(1);
}
}
return arr;
};
```