javascript inheritance by prototype

Question

I was reading this article, and I took the example and made some very small modification

function Parent( p1, p2 ) {
 console.log('run here');
 var prop1 = p1; // private property
 this.prop2 = p2; // public property
 // private method
 function meth1() { return prop1; }
 // public methods
 this.meth2 = function(){ return this.prop2; };
 this.meth6 = function(){ return meth1(); };
}
Parent.prototype.hello=function(){console.log('hi '+this.prop2);};
function Child( p1, p2, p3, p4 ) {
 Parent.apply( this, arguments ); // initialize Parent's members
 this.prop3 = p3;
 this.meth3 = function(){ return this.prop3; }; // override
 var prop4 = p4;
 this.meth4 = function(){ return prop4; };
 }
Child.prototype = new Parent(); // set up inheritance relation
// console.log(Child.prototype)
var cc = new Child( "one", "two", "three", "four" );
console.log(cc)
var result1 = cc.meth6(); // parent property via child
var result2 = cc.meth2(); // parent method via child
var result3 = cc.meth3(); // child method overrides parent method
var result4 = cc.hello(); 
console.log(result1,result2,result3,result4);

The problem is even cc.hello method seems like exist, but when I call it, the console return undefined, can someone please explain why? thanks

• elclanrs: The hello method doesn't return anything, thus undefined. Not sure what you expect...

Answer 1

The method hello doesn't return a value, thus it is undefined

You can change the method to something like this to return the value:

Parent.prototype.hello = function(){
 return 'hi '+ this.prop2;
};

• Sean H: Hahaha, thanks, I guess my brain was short circuited :P