OxfordComma.js -- don't leave home without it.

OxfordComma.js

// Defaults to giving a fuck about an Oxford Comma

var OxfordComma = function(array, gaf) {
  var gaf = (typeof gaf === 'undefined') ? true : gaf;
  var output = "";
  if (array.length <= 1) {
    output = array.toString();
  } else if (array.length == 2) {
    output = array.join(" and ");
  } else {
    var lastItem = array.pop();
    array = array.join(", ");
    if (gaf) {
      output = array + ", and " + lastItem;
    } else {
      output = array + " and " + lastItem;
    }
  }
  return output;
}

// Usage
var edwards = ["Ed","Edd","Eddy"];
console.log(OxfordComma(edwards));