Incorrect.
This loop will make an array look like this [undefined, x1,x2,x3,...xn] at the end;
It would be appropiate to use the following for the loop:
for (var i=numbers.length; i>0; i--){ numbers[i] = numbers[i-1]; }
So the array will look like this [x1,x1,x2,x3,...,xn]