What are objects?
Objects are an extremely important topic in many modern
programming languages, as well as in JavaScript. They dramatically increase
your programming power, richness, effectiveness and efficiency. There are many
tutorials on any part of JavaScript and you are encouraged to browse through
some of them in order to find the ones that explain a particular topic in a way
best for your learning methods and current understanding. Here I talk about
something that will allow you to get into the tutorials on objects easier,
compensating for often neglected efforts in letting students understand the
nature of objects deep enough to be more comfortable with specific
explanations.
Objects are complex data types that might contain data (properties) and a bunch of small
programs (methods). Therefore they
are like combinations of files with data and a library of programs in one
system. Such system can be activated by just its name, can be send somewhere as
one thing and then used in all its aspects, like getting data (properties)
stored in it and/or running some programs that are contained in objects. In
comparison with having files and programs separate – such complex systems (data
types) like objects can be easily created
and handled as one universal package where we can use its functional
capabilities (by running the programs), its data storage capabilities by
adding, changing, and retrieving data, or by both at the same time when newly
obtained by an object data can be processed by its own programs (methods)
either changing its own data or controlling input and output of data processing
in and out of an object.
Object-oriented analysis, design and programming tends to see any real
life object, process, concept, and so on as potential software objects with
their structural and behavioral characteristics. Having these features, program
objects can model real life objects that usually also have properties and can
doo something (or something can be done to them). Examples: a car, a computer,
a pen (with its size and weight, as well as an ability to touch paper, leave a
line of ink, etc.) and so on. Once you are trained in such vision – you can quickly
create models of real situations (or virtual and game situations) and make them interact with each other using
their properties and behaviors in response to initiatives of other objects. Thus
you can create real virtual/game worlds
that react to actions of their own objects or physical objects like players.
Since your software can activate many different objects for communication
with each other – anything that you want object to store, retrieve or do requires
the use of a particular object name because otherwise it will be unclear who
you are talking to (in your command). This
can be achieved by calling first the name of a particular object followed by the
operation on its data or invoking one of its methods (small programs).
ExampleA:
myCar. CurrentMileage = 2000;
ExampleB:
myCar.showYourCurrentMileage();
Here the first example shows how to store data in one of the properties
of myCar object (CurrentMileage), while the second shows how to run a small
program (showYourCurrentMileage()) that might be programmed to get that
property and show it on the page. See below an example from w3schools of an
object “person” and a link allowing to experiment with it by adding and
retrieving more properties.
Example 1. Properties:
<body>
<article id="demo"></article>
<script>
var person = {
firstName : "John",
lastName : "Doe",
age : 50,
eyeColor : "blue"
};
document.getElementById("demo").innerHTML =
person.firstName + " is " + person.age + " years
old.";
</script>
</body>
</html>
Experiment with it live (http://www.w3schools.com/js/tryit.asp?filename=tryjs_create_object1
) by adding and retrieving new properties, like making it say: “John is 50
years old and 4 feet tall.”
Then create more interesting objects with properties and something
printed out about that object. Later you
will be adding code for changing the properties and adding new properties
dynamically.
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