Sorting Arrays (Schwartzian transform)

sortBy.js

/** 
 * Learn about Schwartzian transform
 * https://en.wikipedia.org/wiki/Schwartzian_transform
 */
(function() {
  if (typeof Object.defineProperty === 'function') {
    try {
      Object.defineProperty(Array.prototype, 'sortBy', { value: sortBy });
    } catch (e) {}
  }
  if (!Array.prototype.sortBy) {
    Array.prototype.sortBy = sortBy;
  }

  var _DESC = (/^desc\:\s*/i);

  //comparison criteria
  function _comparer(prev, next) {
    var asc = 1;
    if (typeof prev === "string") {
      if (_DESC.test(prev)) asc = -1;
    }
    if (prev === next) return 0;
    return (prev > next ? 1 : -1) * asc;
  }

  function sortBy(parser) {
    var i, item,
      arrLength = this.length;
    if (typeof parser !== "function") {
      return this.sort(Array.prototype.sort.bind(this));
    }
    //Schwartzian transform (decorate-sort-undecorate)
    for (i = arrLength; i;) {
      item = this[i -= 1];
      //decorate the array
      this[i] = [].concat(parser.call(null, item, i), item);
      //console.log('decorated: ', this[i]);
    }
    //sort the array
    this.sort(function(prev, next) {
      var sorted, length = prev.length;
      for (i = 0; i < length; i += 1) {
        sorted = _comparer(prev[i], next[i]);
        if (sorted) return sorted;
      }
      return 0;
    });
    //undecorate the array
    for (i = arrLength; i;) {
      item = this[i -= 1];
      this[i] = item[item.length - 1];
    }
    return this;
  }
}());

usage.js

//writes the object as string
function write(obj) {
  return JSON.stringify(obj, null, 2);
}

var arr = [494316000000, 415778400000, 346485600000, 494316000000];
console.warn(JSON.stringify(arr));
console.info("DEFAULT SORT (ASC)");
console.log(write(arr.sortBy()));

arr = ["1990/05/12", "1983/03/06", "1980/12/24", "1985/08/31"];
console.warn(JSON.stringify(arr));
console.info("SORT ASCENDING AS Date");
arr.sortBy(function(o) { return new Date(o) });
console.log(write(arr));

console.info("SORT DESCENDING AS String");
arr.sortBy(function(o) { return "DESC:" + o });
console.log(write(arr));

arr = [{ n: 8, d: "1985/08/31" }, { n: 2, d: "1980/12/24" }, { n: 5, d: "1983/03/06" }, { n: 8, d: "1983/03/06" }];
console.warn(JSON.stringify(arr));
console.info("SORT BY @n DESC, AFTER BY @d ASC AS Date");
arr.sortBy(function(o) { return [-o.n, new Date(o.d)] });
console.log(write(arr));

console.info("SORT BY @n ASC, AFTER BY @d DESC AS Date");
arr.sortBy(function(o) { return [o.n, -new Date(o.d)] });
console.log(write(arr));

arr = [{ id: 4, name: "pedro" }, { id: 6, name: "Lucia" }, { id: 7, name: "Paco" }, { id: 3, name: "luis" }];
console.warn(JSON.stringify(arr));
console.info("SORT BY @name ASC (ignore case)");
//toUpperCase() used to ignore case sensitive
arr.sortBy(function(o) { return o.name.toUpperCase() });
console.log(write(arr));

console.info("SORT BY @name DESC (ignore case)");
//toUpperCase() used to ignore case sensitive
arr.sortBy(function(o) { return 'DESC:' + o.name.toUpperCase() });
console.log(write(arr));

arr = [{ id: 4, name: "pedro", age: 26 }, { id: 6, name: "Pedro", age: 32 }, { id: 7, name: "Luis", age: 26 }, { id: 2, name: "luis", age: 26 }];
console.warn(JSON.stringify(arr));
console.info("SORT BY @name ASC (ignore case), AFTER BY @age DESC, AFTER BY @id ASC");
//toUpperCase() used to ignore case sensitive
arr.sortBy(function(o) { return [o.name.toUpperCase(), -o.age, o.id] });
console.log(write(arr));