【译】 javascript 函数参数设计

function VanillaPerson(name, surname) { // multiple arguments
  this.name = name;
  this.surname = surname;
}

var person = new VanillaPerson('Giulio', 'Canti');
person.name; // => 'Giulio'

function Person(obj) { // only one argument
  this.name = obj.name;
  this.surname = obj.surname;
}

var person = new Person({name: 'Giulio', surname: 'Canti'});
person.name; // => 'Giulio'

/**
 ...
 * @param {String} email // change
 ...
 */
function VanillaPerson(name, surname, email) { // change

  // make `new` optional
  if (!(this instanceof VanillaPerson)) {
    return new VanillaPerson(name, surname, email); // change
  }

  this.name = name;
  this.surname = surname;
  this.email = email; // change
}

function Person(obj) {

  if (!(this instanceof Person)) {
    return new Person(obj);
  }

  this.name = obj.name;
  this.surname = obj.surname;
  this.email = obj.email; // change
}

// first argument is name or surname? I don't remember
var person = new VanillaPerson('Canti', 'Giulio'); // wrong!

// order doesn't matter and it's more readable
var person = new Person({surname: 'Canti', name: 'Giulio'});

function VanillaPerson(name, surname, email, vat, address) {
  this.name = name;
  this.surname = surname;
  this.email = email;
  this.vat = vat;
  this.address = address;
}

// I must count the arguments to know where to put 'myaddress'
var person = new VanillaPerson('Giulio', 'Canti', null, 'myaddress'); // wrong!

var person = new Person({surname: 'Canti', name: 'Giulio', address: 'myaddress'});

{
  "name": "Giulio",
  "surname": "Canti"
}

function deserialize(x) {
  return new VanillaPerson(x.name, x.surname);
}

var person = deserialize(json);

var person = new Person(json);

function Person(obj) {

  if (obj instanceof Person) {
    return obj;
  }

  ...
}

var person = new Person({name: 'Giulio', surname: 'Canti'});
new Person(person) === person; // => true

function struct(props) {

  function Struct(obj) {

    // make Struct idempotent
    if (obj instanceof Struct) return obj;

    // make `new` optional, decomment if you agree
    // if (!(this instanceof Struct)) return new Struct(obj);

    // add props
    for (var name in props) {
      if (props.hasOwnProperty(name)) {
        // here you could implement type checking exploiting props[name]
        this[name] = obj[name];
      }
    }

    // make the instance immutable, decomment if you agree
    // Object.freeze(this);

  }

  // keep a reference to meta infos for further processing,
  // documentation tools and IDEs support
  Struct.meta = {
    props: props
  };

  return Struct;

}

// defines a 1-arity Person class
var Person = struct({
  name: String,
  surname: String
});

var person = new Person({surname: 'Canti', name: 'Giulio'});

var person = new VanillaPerson(surname='Canti', name='Giulio');