var order = ['small', 'small', 'medium', 'medium', 'big'];

​

var arr = [

  'small',

  'small',

  'small',

  'small',

  'medium',

  'medium',

  'medium',

  'medium',

  'big',

  'big'

];

​

function orderBy(arr, order) {

  var result = [],

      i = 0, len = arr.length,

      index;

  while (result.length < len) {

    index = arr.indexOf(order[i]);

    result.push(arr[index]);

    arr.splice(index, 1);

    i = i >= order.length-1 ? 0 : ++i;

  }

  return result;

}

​

console.log(orderBy(arr, order));