JavaScript must inherit the of 7js object

Object inherits inherit

var o = { r: };
var c = function f() {
};
c.prototype = o;
c.r = ;
alert(o.r);// The inherited property value has not changed. 
alert(c.r);//c in r Covered o Properties in. 

How do I call the r property in o?

var o = { r: };
var c = function f() {
};
c.prototype = o;
alert(o.r);//  The inherited property value has not changed. 
alert(c.r);// query r Property, return undefined Value. 
alert(c.prototype.r);// c in r Covered o Properties in.  

Calls should be made using prototypes.