<SCRIPT LANGUAGE="JavaScript">
function Shape() {
  this.borderWidth = 5;
}

function Square() {
  this.edge = 12;
}

Square.prototype = new Shape;

myPicture = new Square;

alert(myPicture.__proto__);
alert(myPicture.borderWidth);
</SCRIPT>

The object myPicture has an internal property, __proto__, which is set to Shape when the statement:

Square.prototype = new Shape;

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