sums in node

sum.js

var usage = 'Usage: node sum.js val1 val2 [other_vals]';
var nums = process.argv.slice(2);
var sum = 0;

// as a simple program

console.log(nums);

if (nums.length < 2) {
  console.log(usage);
} else {
  for (var i=0;i<nums.length;i++) {
    // putting a unary operator (+) in front of a variable coerces it into a number
    // see http://xkr.us/articles/javascript/unary-add/ for more info
    sum += +nums[i];
  }
  console.log(sum);
}

// as a function

function getSum(arr) {
  // this `sum`'s scope is the function so it doesn't overwrite the global `sum`
  var sum = 0;

  if (arr.length < 2) {
    // you can also catch errors with try/catch (look it up)
    throw new Error(usage);
  } else {
    for (var i=0;i<arr.length;i++) {
      sum += +arr[i];
    }
    return sum;
  }
}

var result = getSum(nums);

console.log(result);