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Understanding better Javascript OOP architecture [duplicate]

This question already has answers here:
JavaScript: Class.method vs. Class.prototype.method
(5 answers)
Closed 9 years ago.
As i read through some examples of Angularjs' UI add-on, i've stumbled over some code that showed me that my knowdledge of Javascript is quite improvable:
The following is a class inside of an Angular provider:
function Dialog(opts) {
var self = this, options = this.options = angular.extend({}, defaults, globalOptions, opts);
this._open = false;
this.backdropEl = createElement(options.backdropClass);
if(options.backdropFade){
// ...
}
this.handleLocationChange = function() {
self.close();
};
// more functions
}
Pretty straightforward. But outside of that class, there are prototype functions, e.g the above invoked close()
Dialog.prototype.open = function(templateUrl, controller){
var self = this, options = this.options;
// .. some code
};
Now i do not understand why that function is declared as a prototype, but handleLocationChange inside the class itself.
How do i decide which method to choose?
The full gist can be found here

Consider these 2 cases:
Dialog.prototype.open = function...
Dialog.open = function....
First case - every object created by calling new Dialog() will have this open function
Second case has nothing to do with dialog objects, consider it as static function.
EDIT
found a great answer here : javascript-class-method-vs-class-prototype-method

function open will be shared by all objects create using new Dialog().. and handleLocationChange will be different for different objects.

I think handleLocationChange is called from event triggering object that registers listeners but doesn't register the this context so when it's triggered you can't use this as it refers to handleLocationChange. To overcome this they have chosen to set a closure reference to this (=the self variable) and call other instance functions using self. Basically it's storing a value known at creation but not known when handleLocationChange is executing.
Here is some code showing the problem:
var eventSystem={
events:{},
add:function(eventname,fnCallback){
if(!this.events[eventname]){
this.events[eventname]=[];
}
this.events[eventname].push(fnCallback);
},
trigger:function(eventname){
if(!this.events[eventname]){
return;
}
var i=0;
for(i=0;i<this.events[eventname].length;i++){
this.events[eventname][i]();
}
}
};
var person=function(name){
this.name=name;
};
person.prototype.sayName=function(){
console.log("this is now:",this.toString());
// logs this is now: function (){ console.log("this is now:...
// so this is now the sayName function not the person instance
console.log(this.name);//undefined: sayName doesn't have a name property
}
var jon=new person("jon");
eventSystem.add("sayname",jon.sayName);//add event and listener function
eventSystem.trigger("sayname");//trigger the event
Here is how it's solved setting a closure reference
var eventSystem={
events:{},
add:function(eventname,fnCallback){
if(!this.events[eventname]){
this.events[eventname]=[];
}
this.events[eventname].push(fnCallback);
},
trigger:function(eventname){
if(!this.events[eventname]){
return;
}
var i=0;
for(i=0;i<this.events[eventname].length;i++){
this.events[eventname][i]();
}
}
};
var person=function(name){
var self=this;// set closure ref to this
this.name=name;
this.sayName=function(){
console.log(self.name);//use closure ref to get this
// logs jon
}
};
var jon=new person("jon");
eventSystem.add("sayname",jon.sayName);//add event and listener function
eventSystem.trigger("sayname");//trigger the event
Here is a fix to the event system to take care of the this context:
var eventSystem={
events:{},
add:function(eventname,fnCallback,thisRef){
if(!this.events[eventname]){
this.events[eventname]=[];
}
this.events[eventname].push({
"callback":fnCallback,//store the event handler
"thisRef":thisRef//store the this context
});
},
trigger:function(eventname){
if(!this.events[eventname]){
return;
}
var i=0;
for(i=0;i<this.events[eventname].length;i++){
this.events[eventname][i].callback.call(
this.events[eventname][i].thisRef);
}
}
};
var person=function(name){
this.name=name;
};
person.prototype.sayName=function(){
console.log("this is now:",this);//referring to person instance
// with the name jon
console.log(this.name);//logs jon
console.log(this instanceof person);//true
}
var jon=new person("jon");
eventSystem.add("sayname",jon.sayName,jon);//add extra parameter for this ref
eventSystem.trigger("sayname");//trigger the event
The pattern used above is not an event system (think it's pulisher subscriber) as an event usually get triggered on or invoked from an object (button, input, dialog) but in case of a more event system like implementation it would be easy to get the correct this context since you trigger the event on or from an instance (like myButton or myDialog).
See following code for event system like implementation:
var eventSystem={
add:function(eventname,fnCallback){
if(!this.events[eventname]){
this.events[eventname]=[];
}
this.events[eventname].push(fnCallback);
},
//change in trigger as it's passing the event object now
trigger:function(event){
if(!this.events[event.type]){
return;
}
var i=0;
for(i=0;i<this.events[event.type].length;i++){
this.events[event.type][i](event);
}
},
initES:function(){//set the instance variables needed
this.events=this.events||{};
}
};
function addProtos(o,protos){
for(item in protos){
o.prototype[item]=protos[item];
}
}
var person=function(name){
this.name=name;
this.initES();//needed to initialeze eventsystem
};
// make person capable of storing event handlers
// and triggering them
addProtos(person,eventSystem);
person.prototype.askQuestion=function(){
//asking a question will trigger an "answer" event
this.trigger({type:"answer",target:this});
}
// handler for when jon will fire an answer event
function answerHandler(event){
console.log("answer from:",event.target);
console.log("name of the person:",event.target.name);
}
var jon=new person("jon");
jon.add("answer",answerHandler);//add event listener
jon.askQuestion();//triggers the answer event from within jon
jon.trigger({type:"answer",target:jon});//trigger the event externally
Not sure why Angular choose to "break" prototype by using closures as the examples show there are other alternatives. Maybe someone can explain that who is more familiar with Angular.

Is it a good practice to store jquery plugin configuration in data?

I want to create jQuery plugin with config (for example plugin myplugin).
Than call $(elem).myplugin(config); After that I want to call methods from this plugin like $(elem).myplugin().method() with already stored config.
My offer is something like that:
(function($) {
$.fn.myplugin = function(options) {
var $this = $(this);
var getOptions = function() {
return $this.data('myplugin');
};
var initOptions = function(opt) {
$this.data('myplugin', opt);
};
var setOption = function(key, value) {
$this.data('myplugin')[key] = value;
}
var updateBorderWidth = function() {
$this.css('border-width',
getOptions().borderWidth * getOptions().coeficient);
};
var init = function(opt) {
initOptions(opt);
updateBorderWidth();
}
function changeBorder(width) {
setOption('borderWidth', width)
updateBorderWidth();
}
if(options) {
init(options);
}
return {
changeBorder : changeBorder
};
}
})(jQuery);
And usage:
$(function() {
var item1 = $('#test1').myplugin({ coeficient: 1, borderWidth: 1 });
var item1 = $('#test2').myplugin({ coeficient: 2, borderWidth: 1 });
$('#btn').click(updateBorder);
});
function updateBorder() {
$('#test1').myplugin().changeBorder($('#inpt').val());
$('#test2').myplugin().changeBorder($('#inpt').val());
}
Example: http://jsfiddle.net/inser/zQumX/4/
My question: is it a good practice to do that?
May be it's incorrect approach. Can you offer better solution?

Edit:
After searching for threads on jQuery plugin template I found these Boilerplate templates (updated) which are more versatile and extensive designs than what I've offered below. Ultimately what you choose all depends on what your needs are. The Boilerplate templates cover more use cases than my offering, but each has its own benefits and caveats depending on the requirements.
Typically jQuery plugins either return a jQuery object when a value is passed to them as in:
.wrap(html) // returns a jQuery object
or they return a value when no parameter is passed in
.width() // returns a value
.height() // also returns a value
To read your example calling convention:
$('#test1').myplugin().changeBorder($('#inpt').val());
it would appear, to any developer who uses jQuery, as though two separate plugins are being utilized in tandem, first .myplugin() which one would assume will return a jQuery object with some default DOM maniplulation performed on #test1, then followed by .changeBorder($('#inpt').val()) which may also return a jQuery object but in the case of your example the whole line is not assigned to a variable so any return value is not used - again it looks like a DOM manipulation. But your design does not follow the standard calling convention that I've described, so there may be some confusion to anyone looking at your code as to what it actually does if they are not familiar with your plugin.
I have, in the past, considered a similar problem and use case to the one you are describing and I like the idea of having a convenient convention for calling separate functions associated with a plugin. The choice is totally up to you - it is your plugin and you will need to decide based on who will be using it, but the way that I have settled on is to simply pass the name of the function and it's parameters either as a separate .myplugin(name, parameters) or in an object as .myplugin(object).
I typically do it like so:
(function($) {
$.fn.myplugin = function(fn, o) { // both fn and o are [optional]
return this.each(function(){ // each() allows you to keep internal data separate for each DOM object that's being manipulated in case the jQuery object (from the original selector that generated this jQuery) is being referenced for later use
var $this = $(this); // in case $this is referenced in the short cuts
// short cut methods
if(fn==="method1") {
if ($this.data("method1")) // if not initialized method invocation fails
$this.data("method1")() // the () invokes the method passing user options
} else if(fn==="method2") {
if ($this.data("method2"))
$this.data("method2")()
} else if(fn==="method3") {
if ($this.data("method3"))
$this.data("method3")(o) // passing the user options to the method
} else if(fn==="destroy") {
if ($this.data("destroy"))
$this.data("destroy")()
}
// continue with initial configuration
var _data1,
_data2,
_default = { // contains all default parameters for any functions that may be called
param1: "value #1",
param2: "value #2",
},
_options = {
param1: (o===undefined) ? _default.param1 : (o.param1===undefined) ? _default.param1 : o.param1,
param2: (o===undefined) ? _default.param2 : (o.param2===undefined) ? _default.param2 : o.param2,
}
method1 = function(){
// do something that requires no parameters
return;
},
method2 = function(){
// do some other thing that requires no parameters
return;
},
method3 = function(){
// does something with param1
// _options can be reset from the user options parameter - (o) - from within any of these methods as is done above
return;
},
initialize = function(){
// may or may not use data1, data2, param1 and param2
$this
.data("method1", method1)
.data("method2", method2)
.data("method3", method3)
.data("destroy", destroy);
},
destroy = function(){
// be sure to unbind any events that were bound in initialize(), then:
$this
.removeData("method1", method1)
.removeData("method2", method2)
.removeData("method3", method3)
.removeData("destroy", destroy);
}
initialize();
}) // end of each()
} // end of function
})(jQuery);
And the usage:
var $test = $('#test').myplugin(false, {param1: 'first value', param2: 'second value'}); // initializes the object
$test.myplugin('method3', {param1: 'some new value', param2: 'second new value'}); // change some values (method invocation with params)
or you could just say:
$('#test').myplugin(); // assume defaults and initialize the selector

Passing parameters to javascript via data attributes is a great pattern, as it effectively decouples the Javascript code and the server-side code. It also does not have a negative effect on the testability of the Javascript code, which is a side-effect of a lot of other approaches to the problem.
I'd go as far as to say it is the best way for server-side code to communicate with client-side code in a web application.

Closures affecting variables in a closed function within a loop

this.config = {
source: psource,
_events: [
'value1',
'value2',
'value3'
]
};
// Add callbacks to source
var that = this;
for (var i = this.config._events.length - 1; i >= 0; i--) {
var name = this.config._events[i];
console.log(name); // correct
$(this.config.source).on(name, function() {
console.log(name); // value1
console.log(that.config._events[i]); // undefined
});
}
I can't see what is wrong here. I removed all the complicated versions and put in the simplest, it just doesn't want to work at all. The first console.log correctly outputs all the correct names, but it acts like the loop happens all at once, then does it again for the inner console.log's.
Can anyone see what's wrong?

In that block
console.log(that.config._events[i]); // undefined
i would end up being -1 every time your closure is called.
You would have to do something of the sort in order to create a closure around i
$(this.config.source).on(name, function(i) { return function() {
console.log(name); // value1
console.log(that.config._events[i]); // undefined
};
}(i) );

In Javascript, it is not recommended to define a function inside a for loop.
Instead, You should use a javascript lib that provides each e.g. underscore. Then your code will look like this:
_.each(this.config._events, function(e) {
$(this.config.source).on(name, function() {
console.log(e);
});
You might want to reverse the array before.
Here is the doc for _.each
You can also use jQuery's $.each which provides a similar interface.

OO Javascript and this keyword. Object Literals

I'm having issues with Javascript properties and "this" keyword. Forgive me here for asking my third and final JS OOP question. OOP in Javascript has been a headache for me today.
I'm trying to set the property 'source' but the error console is saying it's undefined in parseSource method.
After a little research I believe this.source is is referring to window.source? The code is a boilerplate from Mozilla. When creating extensions init is called by FireFox when the plugin is initialized.
What's the best way to go about setting the properties when creating objects using literal notation?
var myExtension = {
source: null,
init: function() {
// The event can be DOMContentLoaded, pageshow, pagehide, load or unload.
if(gBrowser) {
gBrowser.addEventListener("DOMContentLoaded", this.onPageLoad, false);
}
},
onPageLoad: function(aEvent) {
doc = aEvent.originalTarget; // doc is document that triggered the event
win = doc.defaultView; // win is the window for the doc
// Skip frames and iFrames
if (win.frameElement) return;
this.source = win.document.getElementById('facebook').innerHTML;
myExtension.parseSource();
},
parseSource: function() {
if(this.source == null) {
// So something
} else {
// Do something else
}
}
}
window.addEventListener("load", function() { myExtension.init(); }, false);

When you pass a callback function to gBrowser.addEventListener like this:
gBrowser.addEventListener("DOMContentLoaded", this.onPageLoad, false);
you are passing a reference to the function which is essentially "detached" from the this object where it is defined. So, you need to do something like the following in order to correctly maintain what this references:
init: function() {
var self = this;
if(gBrowser) {
gBrowser.addEventListener("DOMContentLoaded", function () {
self.onPageLoad();
}, false);
}
},
In newer browsers (you did say this is a FF extension), you can use Function.bind to the same effect:
init: function() {
if(gBrowser) {
gBrowser.addEventListener("DOMContentLoaded", this.onPageLoad.bind(this), false);
}
},
Once that's cleared up, you can change the onPageLoad function to:
onPageLoad: function(aEvent) {
doc = aEvent.originalTarget; // doc is document that triggered the event
win = doc.defaultView; // win is the window for the doc
// Skip frames and iFrames
if (win.frameElement) return;
this.source = win.document.getElementById('facebook').innerHTML;
this.parseSource();
},
Edit
A stripped-down demo: http://jsfiddle.net/mattball/bDe6N/

The problem is that methods in Javacript forget about their this if you pass them as a parameter. They only work if you pass them looking like a method
//this doesn't work in JS
f = obj.method
f()
//wtf man! You have to call it looking like a method
obj.method()
In your case this happens because you pass this.onPageLoad as a parameter. Function parameters act like the variable from the last example.
The workaround is to use a wrapper function in order to preserve the method-call appearance
addEventListener( ..., function(){ return this.onPageLoad(); }, ...)
except that this is not lexicaly scoped and the inner function gets a wrong copy as well. After another quick fix we obtain
var that = this;
addEventListener(..., function(){ that.onPageLoad(); }, ...);
This should do the job now.

jQuery: Why would trigger not fire from a JS object?

I've been implementing a form of a publisher/subscriber design pattern in jQuery. I'm basically building classes in Javascript utilizing CoffeeScript that serve as components on my page. i.e. Navigation, DataList, etc.
Instead of having DOM elements fire events, I have instances of these classes that use trigger on themselves to send custom events. These instances can then listen to each other and can update the DOM elements they own accordingly based on the changes in each others behavior!
I know this works as I have one of my components dispatching a custom event properly. However, I've ran into a snag. I've created another component and for the life of me I cannot figure out why it's event is not being fired.
This is the implementation of my class:
window.List = (function() {
List = function(element, settings) {
var _a, _b, _c;
this.list = $(element);
this.settings = jQuery.extend(List.DEFAULTS, settings);
this.links = this.list.find(this.settings.link_selector);
this.links.selectable();
_b = [SelectableEvent.COMPLETED, SelectableEvent.UNDONE, SelectableEvent.SELECTED, SelectableEvent.DESELECTED];
for (_a = 0, _c = _b.length; _a < _c; _a++) {
(function() {
var event_type = _b[_a];
return this.links.bind(event_type, __bind(function(event, selectable_event) {
return this.dispatch(selectable_event);
}, this));
}).call(this);
}
return this;
};
List.DEFAULTS = {
link_selector: "a",
completed_selector: ".completed"
};
List.prototype.change = function(mode, previous_mode) {
if (mode !== this.mode) {
this.mode = mode;
if (previous_mode) {
this.list.removeClass(previous_mode);
}
return this.list.addClass(this.mode);
}
};
List.prototype.length = function() {
return this.links.length;
};
List.prototype.remaining = function() {
return this.length() - this.list.find(this.settings.completed_selector).length;
};
List.prototype.dispatch = function(selectable_event) {
$(this).trigger(selectable_event.type, selectable_event);
return alert(selectable_event.type);
};
return List;
}).call(this);
Pay attention to:
List.prototype.dispatch = function(selectable_event) {
$(this).trigger(selectable_event.type, selectable_event);
return alert(selectable_event.type);
};
This code is triggered properly and returns the expected event type via an alert. But before the alert it is expected to trigger a custom event on itself. This is where I'm encountering my problem.
$(document).ready(function() {
var list_change_handler, todo_list;
todo_list = new List("ul.tasks");
list_change_handler = function(event, selectable_event) {
return alert("Hurray!");
};
$(todo_list).bind(SelectableEvent.COMPLETED, list_change_handler);
$(todo_list).bind(SelectableEvent.UNDONE, list_change_handler);
$(todo_list).bind(SelectableEvent.SELECTED, list_change_handler);
$(todo_list).bind(SelectableEvent.DESELECTED, list_change_handler);
}
You see here the alert "Hurray" is what I want to fire but unfortunately I am having no luck here. Ironically I've done the exact same thing with another class implemented the same way dispatching a custom event and the listener is receiving it just fine. Any ideas on why this wouldn't work?
Update:
Per discussing in the comments, it looks like Logging "this" in console returns the JS Object representing the class. But logging "$(this)" returns an empty jQuery object, thus trigger would never be fired. Any thoughts on why $(this) is coming up empty when "this" is accurately returning the instance of the class?

I found out that jQuery could not index my object because the class implemented it's own version of a jQuery method. In this case, length(). Renaming the length() method to total() resolved the problem completely and any instance of the class can successfully trigger events.