Java Reference
In-Depth Information
Own Properties and Prototype Properties
In the previous example, the object raph had a name property that it inherited from the
constructor function and a weapon property that it inherited from the prototype property.
The object raph has access to both these properties, but the name property is considered
to be its own property while the weapon property is inherited from the prototype object.
Every object has a hasOwnProperty() method that can be used to check if a method is
its own property, or is inherited from the prototype:
<< true
<< false
So what's the difference between own properties and prototype properties? Prototype prop-
erties are shared by every instance of the Turtle constructor function. This means that
they'll all have a weapon property and it will always be the same value. If we create an-
other instance of the Turtle constructor, we'll see that it also inherits a weapon property
that has the same value of "Hands" :
var don = new Turtle("Donatello");
<< {"attack": function (){
return + " hits you with his " + this.weapon;
}, "name": "Donatello", "sayHi": function () {
return "Hi dude, my name is " +;
}, "weapon": "Hands"
<< "Hands"
Every time an instance of the Turtle constructor function calls the weapon property, it
will return "Hands" . This value is the same for all the instances and only exists in one
placeā€•as a property of the prototype object. This means that it only exists in memory in
one place, which is more efficient than each instance having its own value. This is particu-
larly useful for any properties that are the same.
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