have some fun

sum.js

function sum ( args ) {
  var array, sum = 0; // Set vars
  // Conditional to type check what the arguments are
  if ( typeof args == 'number' ) {  // If not an array, then convert it to one.
    array = Array.prototype.slice.call(arguments, 0); // Gotcha, using the key word 'arguments', not the 'args' word. 'arguments' is a special word in javascript that looks like an array, but is not.
  } else {
	  array = args;  
  }

  for ( i in array ) { // I assume recursion could be used here if I knew how recursion worked.
    sum += array[i];
  }  
  return sum; // Must explicity use return or you will get back undefined. 
};

// chat w/ @dhassler

function recur_sum(nums) {
    if (nums.length == 0) { return 0;}
        else if (nums.length == 1) { return nums[0]; }
    else { return nums[0] + recur_sum(nums[1..nums.length]) } 
}

function nth(nums, pos) {
  if (pos > 1) { nth(nums[1..-1], pos--) }
  else { return nums[0]; }
}

nth([10,20,30], 2) // returns 20