Sorting Arrays

## sortBy-old.js
/*
 * Important!
 * This snippet is deprecated, a best implementation of sortBy can be found here:
 * https://github.com/jherax/array-sort-by
 */

var sortBy = (function () {
  var toString = Object.prototype.toString,
      // default parser function
      parse = function (x) { return x; },
      // gets the item to be sorted
      getItem = function (x) {
        var isObject = x != null && typeof x === "object";
        var isProp = isObject && this.prop in x;
        return this.parser(isProp ? x[this.prop] : x);
      };

  /**
   * Sorts an array of elements.
   *
   * @param {Array} array: the collection to sort
   * @param {Object} cfg: the configuration options
   * @property {String}   cfg.prop: property name (if it is an Array of objects)
   * @property {Boolean}  cfg.desc: determines whether the sort is descending
   * @property {Function} cfg.parser: function to parse the items to expected type
   * @return {Array}
   */
  return function sortby (array, cfg) {
    if (!(array instanceof Array && array.length)) return [];
    if (toString.call(cfg) !== "[object Object]") cfg = {};
    if (typeof cfg.parser !== "function") cfg.parser = parse;
    cfg.desc = !!cfg.desc ? -1 : 1;
    return array.sort(function (a, b) {
      a = getItem.call(cfg, a);
      b = getItem.call(cfg, b);
      return cfg.desc * (a < b ? -1 : +(a > b));
    });
  };

}());

## usage.js
//---------------------------
function write(text, array) {
  console.info(`%c${text}`, "color:brown");
  console.log([].concat(array));
}

var aNumbers = [10, 8, 5, 3, 7, 4, 5, 1];
var aObject = [
  { name: "david",  age: 30, date: "2011-11-14T17:25:45Z", achievement: 5 },
  { name: "Luis",   age: 24, date: "2011-11-14T16:30:43Z", achievement: 23 },
  { name: "julian", age: 24, date: "2011-11-31T17:29:52Z", achievement: 12 },
  { name: "alex",   age: 36, date: "2011-11-14T16:58:03Z", achievement: 0 },
  { name: "Samuel", age: 28, date: "2011-11-01T16:17:54Z", achievement: 9 },
  { name: "Diana",  age: 25, date: "2011-11-14T17:07:21Z", achievement: 28 }
];

//---------------------------
console.warn("ARRAY OF NUMBERS");
console.log(aNumbers);

sortBy(aNumbers);
write("ASCENDING ORDER", aNumbers);
// expected: [1, 3, 4, 5, 5, 7, 8, 10]

sortBy(aNumbers, { desc: true });
write("DESCENDING ORDER", aNumbers);
// expected: [10, 8, 7, 5, 5, 4, 3, 1]

//--------------------------
console.warn("ARRAY OF OBJECTS");
console.log(aObject);

sortBy(aObject, { prop: "age" });
write("ASCENDING BY @age", aObject);
// expected:
// [0] = { name: "Luis", age: 24, date: "2011-11-14T16:30:43Z", achievement: 23 }
// [5] = { name: "alex", age: 36, date: "2011-11-14T16:58:03Z", achievement: 0 }

sortBy(aObject, { prop: "achievement", desc: true });
write("DESCENDING BY @achievement", aObject);
// expected:
// [0] = { name: "Diana", age: 25, date: "2011-11-14T17:07:21Z", achievement: 28 }
// [5] = { name: "alex", age: 36, date: "2011-11-14T16:58:03Z", achievement: 0 }

sortBy(aObject, {
  prop: "name",
  // ignores case sensitive
  parser: (item) => item.toUpperCase()
});

write("ASCENDING BY @name", aObject);
// expected:
// [0] = { name: "alex", age: 36, date: "2011-11-14T16:58:03Z", achievement: 0 }
// [5] = { name: "Samuel", age: 28, date: "2011-11-01T16:17:54Z", achievement: 9 }

sortBy(aObject, {
  prop: "date",
  desc: true,
  parser: (item) => new Date(item)
});

write("DESCENDING BY @date", aObject);
// expected:
// [0] = { name: "julian", age: 24, date: "2011-11-31T17:29:52Z", achievement: 12 }
// [5] = { name: "Samuel", age: 28, date: "2011-11-01T16:17:54Z", achievement: 9 }