Writing Scripts in Nashorn - Scripting in Java: Integrating with Groovy and JavaScript - page 113

• It calls the

toString() method on both objects and they print
the same string. This is another case of inheritance. The point
object does not set its prototype, so its prototype is, by default,
set to Object.prototype object, where Object is a built-in object
in Nashorn. The toString() method is defined in Object.
prototype and it is inherited by default by all objects. The
coloredPoint object inherited it from the point object and the
point object inherited it from the Object.prototype object.
Finally, it compares the prototypes of objects and prints the •

results. The output confirms the prototype chain as discussed.

Figure 4-1 depicts the prototype chain for the point and coloredPoint objects.
Notice that the Object.prototype has its prototype set to null , indicating the end of
the prototype chain. You could have set the prototype for the point object to null , thus
eliminating the Object.prototype from the prototype chain.

Figure 4-1. The Prototype Chain for the point and coloredPoint Objects

In the previous example, you saw that the two objects shared the same properties
named x and y . You do not really want to share object's states. Typically, you want
each object to have its own state. You could have solved this problem by redeclaring
the x and y properties in the coloredPoint object. If you set the x and y properties on
coloredObject , coloredObject will get new x and y properties of its own. The following
demonstrates this:

var point = {x: 10,
y: 20,
print: function() {
printf("(%d, %d)", this.x, this.y);
}
};

var coloredPoint = {color: "red",
print: function() {
printf("(%d, %d, %s)", this.x,
this.y, this.color);

}
};