Which datastructure is this? - Javascript

Question

I came across a code snippet in JS

globe =
{
   country : 'USA',
   continent : 'America'
}

Using the variable declared above by:

alert(globe.country);

Questions:

Is this a JS class with 2 members?
Why is the var keyword not used when declaring globe?
If it's a class, can I have member functions as well?

Thanks

geowa4 · Accepted Answer · 2009-09-08 17:42:54Z

11

That is a JS object with two properties.
Not using var places the variable in the global scope
Though not a class, it can still have functions as properties

The functions can be tacked on two different ways:

globe.myFunc = function() { /* do something */ };

or

globe = {
    ...
    myFunc: function() { /* do something */ }
}

answered Sep 8, 2009 at 17:42

geowa4

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6 Comments

Nick Over a year ago

My background is in C#. In C#, an object is an instance of a class. It appears that in JS, the class is called as an object?

geowa4 Over a year ago

js has no "class". it only has objects. functions are first-class objects and new "instances" can be created using the new keyword.

meder omuraliev Over a year ago

there are no classes in ECMAScript; you can mimic the functionality of a class by defining a constructor function and using the new keyword to create objects. I suggest familiarizing yourself with prototypal inheritance.

Will Hartung Over a year ago

JS doesn't have formal classes, it just has objects and uses a prototype based inheritance system. You should do more research in to how JS represents objects, how its prototype inheritance works, and how some mimic more conventional class based OO techniques built on top of JS's system.

Nick Over a year ago

Thanks, I will definitely look into the inheritance system. If I were to compare any OOP language to JavaScript, which of these have native support in JS (or can be mimicked in some way) - Abstraction, Polymorphism, Inheritence, Encapsulation?

|

Lark · Accepted Answer · 2009-09-08 17:42:21Z

3

That is a JavaScript object. Written in the object literal notation.

answered Sep 8, 2009 at 17:42

Lark

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Comments

Amok · Accepted Answer · 2009-09-08 17:54:21Z

1

JavaScript is not an object-oriented language so there are not classes in the same sense as in a language like Java or C#. JavaScript is a prototype based language. So this is an object with two members. You can add additional members like you would to any other object and they can be functions.

answered Sep 8, 2009 at 17:54

Amok

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