Why/How should I used objects in JavaScript?

Question

I understand how to instantiate objects and call them, but I just cannot find a reason to use them in my script. I could do

var obj = {
    hi: function() {
        return "Hello";
    }
}; 

but why can't I just do it the same way like:

function hi() {
    return "Hello";
}

I've never understood the reasons why I should use prototyping either. Most of the things I do in JavaScript I can do well without objects. But I want to use objects. What are objects for and what are the reasons why I should use them?

Answer 1

In your simple example, it makes indeed no sense to write a semi "class" / object to hold that method. But when your code grows, you're getting more and more functions and methods, you don't really want to have them all in one big (global) namespace. That is just so impossible to maintenain, no one will understand that code including you at some later point.

That is the first good reason to wrap methods together in an object/"class". Another good reason is re-usabilty. If you're writting objects which are able to inherit their methods, you can re-create another object and abstract it from there on. Most simple concept, but you want to use it if you're describing "things" in your application as module/object.

Answer 2

Objects are useful for example for making a single unit out of values that belong together. Example:

function Person(firstName, lastName, gender, age) {
  this.firstName = firstName;
  this.lastName = lastName;
  this.gender = gender;
  this.age = age;
}

Person.prototype = {
  getFullName: function() { return this.firstName + ' ' + this.lastName; },
  isMale: function() { return this.gender == 'Male'; },
  isFemale: function() { return this.gender == 'Female'; }
};

var amanda = new Person('Amanda', 'Smith', "Female", 42);
var john = new Person('John', 'Doe', 'Male', 72);

alert(amanda.getFullName());
alert(john.isMale());

Compared to the less structured:

function getFullName(firstName, lastName) {
  return firstName + ' ' + lastName;
}

function isMale(gender) {
  return gender == 'Male';
}

function isFemale(gender) {
  return gender == 'Female';
}

var amandaFirstName = 'Amanda';
var amandaLastName = 'Smith';
var amandaGender = 'Female';
var amandaAge = 42;
var johnFirstName = 'John';
var johnLastName = 'Doe';
var johnGender = 'Male';
var johnAge = 72;

alert(getFullName(amandaFirstName, amandaLastName));
alert(isMale(johnGender));