Create a model (POJO) in JavaScript

Question

can you help me with a doubt?

I'm trying an approach more didatical in JS, creatind a POJO/POCO for a model class.

I have a Person object:

function person(name, age, gender) {
      this.name = name;
      this.age = age;
      this.gender = gender;
      return this;
}

Now I can create some data:

var personalities = new Array(new person("Alicia", 152, "F"), 
                              new person("Bartolomeu Simpson", 36, "M"),
                              new person("Ayrton Senna", 58, "M"),
                              new person("Jean J. Michel", 36, "M"),
                              new person("Jean J. Michel", 37, "M"));

Well, done it if I call sort method there is no action to order this data:

personalities.sort();

for(var i = 0; i < personalities.length; i++)
  console.log(personalities[i].name);

Output is:

Alicia
Bartolomeu Simpson
Ayrton Senna
Jean J. Michel
Jean J. Michel

I created a toString() method:

function person(name, age, gender) {
  this.name = name;
  this.age = age;
  this.gender = gender;

  this.toString = function() {
    return this.name + " " + 
           this.age + " years old" + 
           (this.gender == 'M' ? " man" : " woman");
  };

  return this;
}

Now the sort method is "ok", the output now is:

Alicia
Ayrton Senna
Bartolomeu Simpson
Jean J. Michel
Jean J. Michel

But I want do something different, order by name and age (oldest first). I implemented the method compareTo(obj):

function person(name, age, gender) {
  this.name = name;
  this.age = age;
  this.gender = gender;

  this.toString = function() {
    return this.name + " " + 
           this.age + " years old" + 
           (this.gender == 'M' ? " man" : " woman");
  };

  this.compareTo = function(otherPerson) {
    var resultOfComparison = 0;

    if(this.name > otherPerson.name) {
      resultOfComparison = 1;
      return resultOfComparison;
    }
    else if(this.name < otherPerson.name) {
      resultOfComparison = -1;
      return resultOfComparison;
    }
    else if(this.age > otherPerson.age) {
      resultOfComparison = -1;
      return resultOfComparison;
    }
    else if(this.age < otherPerson.age) {
      resultOfComparison = 1;
      return resultOfComparison;
    }

    return resultOfComparison;
  };

  return this;
}

The method is ok, look it:

var jean1 = new person("Jean J. Michel", 36, "M");
var jean2 = new person("Jean J. Michel", 37, "M");

console.log(jean1.compareTo(jean2)); //1
console.log(jean1.compareTo(jean1)); //0
console.log(jean2.compareTo(jean1)); //-1

Can I use this approach to sort my array? Something like this:

personalities.sort(person.compareTo);

I really do not want to do it in a service class that use my model:

personalities.sort(function(personA, personB) {
                     var resultOfComparison = 0;

                     if(personA.name > personB.name) {
                       resultOfComparison = 1;
                       return resultOfComparison;
                     }
                     else if(personA.name < personB.name) {
                       resultOfComparison = -1;
                       return resultOfComparison;
                     }
                     else if(personA.age > personB.age) {
                       resultOfComparison = -1;
                       return resultOfComparison;
                     }
                     else if(personA.age < personB.age) {
                       resultOfComparison = 1;
                       return resultOfComparison;
                     }

                     return resultOfComparison;
                   });

I think that this is a model responsibility.

Thanks for all help.

Answer 1

Well, the comparator function you pass to sort() needs to take two arguments, so it can't be an instance method. I'd suggest you define it as a "static" method:

function person(name, age, gender) {
    this.name = name;
    this.age = age;
    this.gender = gender;
}

person.compare = function(personA, personB) {
    if(personA.name > personB.name) return 1;
    if(personA.name < personB.name) return -1;
    return personB.age - personA.age;
}

And then you can call it when you sort:

personalities.sort(person.compare);

I hope I understood correctly what you were asking.