Major Differences between C# and Unity JavaScript - Unity 3 Game Development - page 334

Class declarations
You can define classes in JavaScript, in a similar way as you do it in C#. The following example
is a class that inherits from MonoBehaviour .
JavaScript:
class MyClass extends MonoBehaviour {
var myVar = 1;
function Start() {
Debug.Log("Hello World!");
}
}
C#:
class MyClass : MonoBehaviour {
public int myVar = 1;
void Start() {
Debug.Log("Hello World!");
}
}
However in JavaScript, if you're inheriing from MonoBehaviour , you don't need to write a
class body at all. You can also write the following script in JavaScript, which will get a similar
result as the preceding JavaScript:
var myVar = 1;
function Start() {
Debug.Log("Hello World!");
}
Unity will automaically implement an explicit class body for you.
You can also write classes that do not inherit from anything; however, you can't place these
scripts on the game objects—you have to instaniate them with the new keyword.
JavaScript:
class MyClass {
var myVar = 1;
function MyClass() {
Debug.Log("Hello World!");
}
}