Flatten & Sort in JavaScript

gistfile1.txt

(function() {
  var flattenAndSort = function(input) {
    function flatten(input) {
      return input.reduce(function(flattened, currentPart) {
        return flattened.concat(Array.isArray(currentPart) ? flatten(currentPart) : currentPart);
      }, []);
    };
    return flatten(input).sort();
  }

  var output = flattenAndSort( ["gamma", ["alpha", ["beta"]], [[["delta"]]]] );
  var expectedOutput = ["alpha", "beta", "delta", "gamma"];
  console.log(output);
  console.log(expectedOutput);
  console.assert(JSON.stringify(output) === JSON.stringify(expectedOutput), 'Failed to match!');
})();