[рони]

sizoider,

function fn(arr, p, n)
      {  var c =  []
         for (var i=1; i<p; i++)  {c = c.concat(arr.slice())}
         return c.concat(arr.slice(0,++n))
      }
     alert(fn([1,2,3,4,5], 2, 2));
     alert(fn([1,2,3,4,5], 3, 2));