Java Reference
In-Depth Information
To create an instance of the
Dice
object, invoke the constructor function using the
new
operator:
var red = new Dice();
<< {"roll": function () {
return Math.floor(this.sides * Math.random() + 1)
}, "sides": 6}
The function returned an object that was assigned to the variable
red
, which is said to be
an instance of the
Dice
constructor function. We can confirm this using the
instanceof
operator:
red instanceof Dice
<< true
This means that it will have a
sides
property and
roll()
method:
red.sides;
<< 6
red.roll();
<< 4
Warning: Use
new
Make sure that you use the
new
operator when employing a constructor
function to instantiate a new object. Otherwise, you'll actually just call the
function itself, and will assign the variable to the return value of the func-
tion (which is usually undefined):
var yellow = Dice();
<< undefined
yellow.sides
<< Error: "yellow is undefined"
