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JavaScript Object-Oriented JavaScript: Challenge Building Constructor Methods and Generating Objects Player Properties Solution

Alex Hort-Francis
Alex Hort-Francis
17,074 Points

Best practice for declaring properties within a class?

In the video, Ashley declares the empty array tokens in the constructor of the Player class.

Testing with the console in the browser, I can see that declaring it in the body of the class is also accepted: it returns a value when an object is instantiated.

I wonder what is considered best practice for declaring properties: declaring in the constructor method like this:

class Player {
  constructor(){
   this.tokens = [];
  }
}

... or in the class body, like this:

class Player {
  constructor(){}
  tokens = [];
}

Obviously we wouldn't be able to pass in a value to the property upon instantiation unless it were declared in the constructor, but if we were planning to use a setter method to provide a value after instantiation instead then is there any benefit to declaring the empty property in the constructor method?

1 Answer

Steven Parker
Steven Parker
229,017 Points

Like many things in programming, it's programmer's choice. But the 2nd form is a bit more concise, and it can be even more so if you leave off the definition of the empty constructor completely.

I might prefer the first form if there were to be other instance variables initiated in the constructor, just to keep them all together.

Alex Hort-Francis
Alex Hort-Francis
17,074 Points

That's a very good answer; I agree with your logic.

Ah so we don't technically need a constructor? Interesting.

Quite dynamic then, Javascript..