JavaScript - Help Understanding Inheritance And Nested Objects (non-dom Related)

This is a little hard to explain so I'm posting an example.

Code:

//NESTED FUNCTION I'M USING TO DEMONSTRATE MY QUESTION
function foo(a) {
this.x = 5;

//USED TO SET THE VALUE OF X
if( a == 0 ) 
   return function(z) {
      return x = z;
   }

//USED TO RETRIEVE THE VALUE OF X
else if( a == 1 )
   return function() {
      return x;
   }

}


//MAKES setX THE SETTER FUNCTION
var setX = foo(0);
//MAKES getX THE GETTER FUNCTION
var getX = foo(1);

print( "setX(25), not an instance: " + setX( 25 ) );
print( "getX(), not an instance: " + getX() );

print( "" );
//CREATES AN OBJECT INSTANCE USING FOO AS CONSTRUCTOR
var q = new foo();
print( "value of x in object instance: " + q.x );
print( "" );

print( "setX(25), not an instance: " + setX( 25 ) );
print( "getX(), not an instance: " + getX() );

This code will output:
Code:

setX(25), not an instance: 25
getX(), not an instance: 25

value of x in object instance: 5

setX(25), not an instance: 25
getX(), not an instance: 25

Observations:
It seems like this.x actually has two meanings.
1)x becomes a member of the "Function" object foo().
2)x becomes a part of the constructor for prototype class foo.

But why then does x revert back to the original value of 5 when I use foo as a constructor? Does javascript automatically save the original value on creation for a reason?


What is going on behind the scenes to make this happen? Is this behavior part of an ontological model that makes sense?


Similarly, if I change "this.x" to "var x" I can access the value of x but I can't change it. Not that that I should be able to, the syntax "var x" doesn't make x a member of foo anyway. But I'm still having trouble classifying the relationship "var x" has to the function. Anyways this is more of a tangent. My main question is above but if anyone has something to say about this, I'd be interested to hear it.

It seems like all these behaviors have rules to them, but there is no conceptual model to think through that guide these behaviors. Or maybe I'm just ignorant. Enlighten me.

What are the benefits of prototypal inheritance over classical inheritance?

What are the benefits of prototypal inheritance over classical inheritance?

Hello All,

can someone pls help me with the error shown in firebug for the code below:

Firebug error:
Object.method is not a function
Object.method('superior', function (name) {

Constructor functions work until it gets to /* Super method template */.
Thats where the error comes from. Code is from javascript - good parts.

var mammal = function(spec) {
var that = {};

that.get_name = function() {
return spec.name;
}

that.says = function() {
return spec.saying || '';
}

return that;
}

var myMammal = mammal({name: 'Herbie', saying: 'Im herb the mammal'});

console.log(myMammal.get_name());
console.log(myMammal.says());


var cat = function(spec) {
spec.saying = spec.saying || 'Meow!'

var that = mammal(spec);

that.purr = function(n) {
var i, s = '';

for(i=0; i < n; i +=1) {
if(s) {
s += '-';
}

s += 'r'
}
return s;
}

that.get_name =function() {
return that.says() +' '+ spec.name +' '+ that.says();
}
return that;
}

var myCat = cat({name: 'Henrietta!', saying: 'Im a pussycat'})
console.log(myCat.get_name());
console.log(myCat.purr(3));


/* Super method template */
Object.method('superior', function (name) {
var that = this,
method = that[name];
return function ( ) {
return method.apply(that, arguments);
};
});


/* Super method e.g. */

var coolcat = function (spec) {
var that = cat(spec),
super_get_name = that.superior('get_name');
that.get_name = function (n) {
return 'like ' + super_get_name( ) + ' baby';
};
return that;
};

var myCoolCat = coolcat({name: 'Bix'});
console.log(myCoolCat);
var name = myCoolCat.get_name();
console.log(name);

I'm trying my best to figure this out with google, but I've found 4 different syntaxes and can't get any of them to work. I need to have several classes extend another for my chess game. I need classes, Rook, Knight, Bishop etc... all extend from class Piece. can anyone help me with the syntax

var Piece = Class.create();
Piece.prototype = {
initialize: function(src, square){
//init stuff here
},
setSqua function(square){
//sets the square of the piece
},
}

Rook.prototype = new Piece();
function Rook(src, square) {
Piece.apply(src, square);
}

Thanks to anyone who helps

Hi, I would like to know which is the best approach when trying inheritance with js - module pattern. In the example below, I want that parent.hi() be fired from child:


Code:

var parent = function(){
    return{
        hi: function(){
            console.info('hi');
        }
    }
}();

var child = function(){
    

    return{
        bye: function(){
            console.info('bye');
        },
        hi: function(){//look he 
            
            parent.hi();    

        }   
    }
}();


child.hi();

Is there a better way to do this ?

Thanks in advance

First class:
Code:

function ClassOne(){    
    this.events = [];
    this.executeEvents = [];
    this.addEvents = function(event){
        this.events.push(event);
    }
    this.addExecuteEvents = function(e){
        this.executeEvents.push(e)
    }
    this.getEvents = function(){
        return this.events;
    }
}

Second class:

Code:

function ClassTwo(){
    this.add = function(e){
        this.addEvents(e)
    }
}
ClassTwo.prototype = new ClassOne

Here the second class extends the first class,
now I want to create two objects of class two,
Code:

 var b = new ClassTwo();
 b.add('hello');
 var c = new ClassTwo();
 c.add('hi');
 console.log(c.getEvents())

I just added one event on b and c each, but when I logged the c.getEvents(), it returns both 'hi' and 'hello' events. why??
What am I doing wrong?? how to solve this problem??

Thanks in advance

Hi!

This is probably a classic inheritance thing...

I have two objects, C1 and C2. Both contains a callback method named 'callback'. Now, if I let C2 inherit from C1, then C1's 'callback' gets overridden by C2's. The problem is I still want C1's methods to access their own 'callback' method.

Is this possible, and is it "valid"? Am I headed down disaster lane here? Should I re-think and refactor?


Example:

Code:

function C1 () {};

C1.prototype.callback = function () {
	console.log('c1 called');
};

C1.prototype.call = function () {
	//do stuff
	this.callback();
};

function C2 () {};

C2.prototype = new C1();

C2.prototype.callback = function () {
	console.log('c2 called');
};


var obj = new C2();
obj.call();

Output:
c2 called Regards

Don

please bear with my noobishness, but i've been trying for many hours to understand what is going on behind this code:


**
Code:

function Person() {
document.write('constructor: <br/>'+this.constructor); //displays Person constructor
this.name = "Rob Roberson";
this.age = 31;
}

function Employee() {
document.write('<br/>constructor: <br/>'+this.constructor); //displays Person constructor
this.dept = "HR";
this.manager = "John Johnson";
}

Employee.prototype = new Person();

var Ken = new Employee();

document.write('<br/>'+Ken.constructor); //displays Person constructor
document.write('<br/>name:'+ Ken.name + '<br/>age:' + Ken.age + '<br/>dept:' + Ken.dept + '<br/>manager:' + Ken.manager ); //displays all properties correctly

***

from what i've read, every object references a prototype. in this case, the Employee function will automatically reference a prototype with 'constructor' as its initial value. this command:

Employee.prototype = new Person();

will replace the Employee function's prototype to an instance of Person. so now Employee function's prototype will contain both name and age properties, BUT, and this is where i get lost, ITS CONSTRUCTOR PROPERTY GETS REPLACED! so how does:

var Ken = new Employee();

actually construct an instance of Employee if the reference to its constructor has been replaced by an instance of Person that only contains name and age properties? how is Ken ever initialized by Employee constructor?

Okay so if you go to this website:

http://gameusd.com/

You can pick your game & country -- say its world of warcraft US

And then you pick your realm and faction, and then it gives you the prices on those particular realms/factions.

What i wanted to know was if it was possible to somehow make a program that fetches the prices of EVERY single realm/faction and lists them all side by side and in order of lowest to highest price or whatever. Would massively appreciate if somehow could tell me if its possible. Because obviously doing it all manually would be a huge pain in the *** and take hours.

Hi Friends,
i have a smal task i.e
i have textbox1 ,botton,textbox2 when i enter 21 value then i click button its get in sama row values in textbox2.
i have xml file like this
<DATAPACKET >
<ROWDATA>
<R_ID>101</R_ID>
<R_NAME>R-12</R_NAME>
<R_TEMP>4.266</R_TEMP>
<R_COLOR>White</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>20</R_ID>
<R_NAME>R-22</R_NAME>
<R_TEMP>4.266</R_TEMP>
<R_COLOR>Green</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>21</R_ID>
<R_NAME>R-32</R_NAME>
<R_TEMP>4.266</R_TEMP>
<R_COLOR>White</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>104</R_ID>
<R_NAME>R-134A</R_NAME>
<R_TEMP>4.246</R_TEMP>
<R_COLOR>Light Blue</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>21</R_ID>
<R_NAME>R-290</R_NAME>
<R_TEMP>4.246</R_TEMP>
<R_COLOR>White</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>31</R_ID>
<R_NAME>R-401A</R_NAME>
<R_TEMP>4.246</R_TEMP>
<R_COLOR>Pink</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>32</R_ID>
<R_NAME>R-401B</R_NAME>
<R_TEMP>4.264</R_TEMP>
<R_COLOR>White</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>108</R_ID>
<R_NAME>R-402A</R_NAME>
<R_TEMP>4.426</R_TEMP>
<R_COLOR>Light Greem</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>129</R_ID>
<R_NAME>R-402B</R_NAME>
<R_TEMP>4.266</R_TEMP>
<R_COLOR>White</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>110</R_ID>
<R_NAME>R-404A</R_NAME>
<R_TEMP>4.246</R_TEMP>
<R_COLOR>Orange</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>121</R_ID>
<R_NAME>R-407A</R_NAME>
<R_TEMP>4.267</R_TEMP>
<R_COLOR>White</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>122</R_ID>
<R_NAME>R-408A</R_NAME>
<R_TEMP>4.267</R_TEMP>
<R_COLOR>White</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>113</R_ID>
<R_NAME>R-409A</R_NAME>
<R_TEMP>4.267</R_TEMP>
<R_COLOR>White</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>134</R_ID>
<R_NAME>R-407C</R_NAME>
<R_TEMP>4.264</R_TEMP>
<R_COLOR>White</R_COLOR>
</ROWDATA>
<ROWDATA>
<R_ID>115</R_ID>
<R_NAME>R-410A</R_NAME>
<R_TEMP>4.426</R_TEMP>
<R_COLOR>White</R_COLOR>
</ROWDATA>
</DATAPACKET >
then i try this hear i get all values
function gettxt() {
results = new Array;
var searchterm = document.getElementById("searchme").value;
if (searchterm == null || searchterm == "") {
alert("Enter textbox value");
return false;
}
var istrlen1 = searchterm.length;
var tempname1;
if (istrlen1 == 1) {
tempname1 = searchterm;
}
if (istrlen1 == 2) {
tempname1 = searchterm;
}
if (istrlen1 == 3) {
tempname1 = searchterm;
}
if (istrlen1 == 4) {
tempname1 = searchterm;
}
for (i = 0; i < x.length; i++) {
var name = x[i].getElementsByTagName("R_ID")[0].firstChild.nodeValue;
var name1 = x[i].getElementsByTagName("R_NAME")[0].firstChild.nodeValue;
var exp = new RegExp(tempname1, "i");
if (name.match(exp) != null) {
y = y + 1;
results.push(name1);
}
}
textbox2.value = results;
}
i try the above code hear small problom when i enter 21 and click button its display 21,121,123... related values i dont want like that
for example textbox1=21 buttonclick textbox2=R-32,r-407A,r-408A like that i dont want like that
i want textbox1=21 buttonclick textbox2=R-32 only in same row value
please any one knows well in js please resolve my problom

Hi guys, Im not sure my subject decsription gives an exact description of what i am after but i will try and explain my requirements a bit better.

I have an header menu there are items in this menu but there are a lot of them and if you try view on a normal 1024 x 760 you have to horizontal scroll to view all the items, but on my monitor 1920 x 1080 it is fine.
I don't want to do it this way since I hate having to scoll both horizontal and vertical. I would like to be able to change the items on this header to become a rollover dropdown menu when they would normally be hidden becuase of the screen width. I have seen this done before I am just unsure about how to implement this.

can anyone point me in the direction of some good resources for this?

Thanks

EDIT----------------------------------------------------------------------------------------------

I am using jQuery if that make it easier to fine a script that would do this

im new to webpage programming,but do hav some basic c/c++ programming skill. in order for me to understand the following codes, what should i read?
i had read thru w3schools.com html and javascript tutorials but it is stil difficult for me to understand the codes,can somebody help me?thanks!


Code:

function getQuery() {
                var scoping             = "&project=${currentProject}&projectScopeUp=" + projectScopeUp + "&projectScopeDown=" + projectScopeDown;
                var paging              = "&pagesize=100";
 
                return {
                    "currentProject"   : "/iteration:current/project",
                    "#storyType"        : "/typedefinition?query=(Name = \"Hierarchical Requirement\")",
 
                    "taskUnit"          : "${iteration/workspace/workspaceConfiguration/taskUnitName}",
                    "storyStates"       : "${#storyType/attributes[name=schedule state]/allowedvalues/stringvalue}",
 
                    "iteration"         : "/iteration:current?fetch=name,objectid&order=StartDate",
                    "iterations"        : "/iterations?fetch=name,objectid&order=StartDate,Name&project=${currentProject}&projectScopeUp=false&projectScopeDown=false" + paging,
 
                    "users"             : "/users?fetch=displayname,loginname,emailaddress,objectid" + paging,
 
                    "tasks"             : "/tasks?fetch=taskindex,name,objectid,formattedid,owner,blocked,estimate,todo,actuals,state,workproduct&query=(Iteration = ${iteration})" + scoping + paging,
 
                    "stories"           : "/hierarchicalrequirement?fetch=rank,blocked,formattedid,name,objectid,owner,project,schedulestate,taskestimatetotal,taskremainingtotal,taskactualtotal,tasks&order=Rank&query=(Iteration = ${iteration})" + scoping + paging,
                    "defects"           : "/defect?fetch=rank,blocked,formattedid,name,objectid,owner,project,schedulestate,taskestimatetotal,taskremainingtotal,taskactualtotal&order=Rank&query=(Iteration = ${iteration})" + scoping + paging,
                    "defectsuite"       : "/defectsuite?fetch=rank,blocked,formattedid,name,objectid,owner,project,schedulestate,taskestimatetotal,taskremainingtotal,taskactualtotal&order=Rank&query=(Iteration = ${iteration})" + scoping + paging,
                    "testsets"          : "/testset?fetch=rank,blocked,formattedid,name,objectid,owner,project,schedulestate,taskestimatetotal,taskremainingtotal,taskactualtotal&query=(Iteration = ${iteration})" + scoping + paging
                };
            }