Variadic sort

sort.js

function getTestPeople() {
  return [{
    name: "Kylie",
    age: 18
  }, {
    name: "Andrew",
    age: 23
  }, {
    name: "Andrew",
    age: 18
  }, {
    name: "Clay",
    age: 23
  }];
}

function sort() {
  var sortFunctions = Array.prototype.slice.call(arguments);
  var lastArgument = sortFunctions.pop();
  
  if (lastArgument.sort) {
    return lastArgument.sort(function(a, b) {
      for (var i = 0; i < sortFunctions.length; i++) {
        var order = sortFunctions[i](a, b);
        if (order !== 0) {
          return order;
        }
      }
      return 0;
    });
  }
  
  return sortFunctions.reduce(function(bound, arg) {
    return bound.bind(this, arg);
  }.bind(this), sort).bind(this, lastArgument);
}

function byName(a, b) {
  if (a.name > b.name) {
    return 1;
  } else if (a.name < b.name) {
    return -1;
  }
  return 0;
}

function byAge(a, b) {
  return a.age - b.age;
}

var sortByAgeThenName = sort(
  byAge,
  byName
);

var sortByNameThenAge = sort(
  byName,
  byAge
);

console.log('By Age Then Name');
console.log(JSON.stringify(sortByAgeThenName(getTestPeople()), null, 2));

console.log('By Name Then Age');
console.log(JSON.stringify(sortByNameThenAge(getTestPeople()), null, 2));