circular_range.js

var arr = [0,1,2,3,4,5,6,7,8,9];

/**
 * Returns a circular range of an Array 
 * @param index {Number} starting position
 * @param size {Number} size of the range
 * @param [position] {Number} position of the range, negative values will return a range before the index
 * @return {Array}
 **/
Array.prototype.range = function(index, size, position){
        // make a copy
    var a = this.slice(), 
        // if index is out of bound start counting from 0
        f = index % a.length;
    return (position < 0? a.splice(f - size + 1, size):a.splice(f)).concat(a).splice(0, size);
}

console.log(arr.range(9, 4)); // [9, 0, 1, 2]
console.log(arr.range(1, 4, -1)); // [8, 9, 0, 1]