How to add functions to some jQuery objects, but not others? - javascript

Let's say I have a <ul> list:
<ul class="products">
...
</ul>
I want to select it with jQuery, then add some functions to that object. For example, I'd like to add an addProduct(productData) function and a deleteProduct(productId) function. However, I'd like the functions to only be added to the object that's returned by the selector. So for example, something like this:
var productList = $.extend($('ul.products'), {
addProduct: function(productData) {
// add a new li item
},
deleteProduct: function(productId) {
// delete li with id
}
});
How would I do this using jQuery? The key point here is that I only want to add the functions to an instance returned by a jQuery selector. In other words, I don't want to modify jQuery's prototype or create a plugin, since those will make the functions available across everything, whereas I only want to add the functions to one specific instance.

If you only want the addProduct and deleteProduct methods to feature on that single jQuery object, then what you've got will work fine; but you'll have to keep a reference to that jQuery object/ only use it once, to preserve the existance of the addProduct and deleteProduct methods.
However, these addProduct and deleteProduct methods are unique to that particular jQuery object; the methods won't exist on any other jQuery objects you create;
var productList = $.extend($('ul.products'), {
addProduct: function(productData) {
// add a new li item
},
deleteProduct: function(productId) {
// delete li with id
}
});
// Using this particular jQuery object (productList) will work fine.
productList.addProduct();
productList.removeProduct();
// However, addProduct() does not exist on new jQuery objects, even if they use
// the same selector.
$('ul.products').addProduct(); // error; [object Object] has no method 'addProduct'
The best way do to this would be to go-back-to-basics and define separate addProduct and deleteProduct functions, which accept a jQuery object. If you wanted to restrict these functions to they only worked on the ul.products selector, you could do;
function addProduct(obj) {
obj = obj.filter('ul.products');
// do something with `obj` (its a jQuery object)
}
This approach would be recommended as it keeps the jQuery.fn API consistent; otherwise you'd be adding addProduct and removeProduct to some jQuery.fn instances but not others, or making their usage redundant in others. With this approach however addProduct and removeProduct are always there, but don't get in anyones way if they don't want to use them.
Historical Notes
This answer was originally written in November 2011, when jQuery 1.7 was released. Since then the API has changed considerably. The answer above is relevant to the current 2.0.0 version of jQuery.
Prior to 1.9, a little used method called jQuery.sub used to exist, which is related to what you're trying to do (but won't help you unless you change your approach). This creates a new jQuery constructor, so you could do;
var newjQuery = jQuery.sub();
newjQuery.fn.addProduct = function () {
// blah blah
};
newjQuery.fn.deleteProduct = function () {
// blah blah
};
var foo = newjQuery('ul.products');
foo.deleteProduct();
foo.addProduct();
var bar = jQuery('ul.products');
bar.deleteProduct(); // error
bar.addProduct(); // error
Be careful though, the $ method alias would reference the old jQuery object, rather than the newjQuery instance.
jQuery.sub was removed from jQuery in 1.9. It is now available as a plugin.

You can make your own jQuery methods as follows:
$.fn.addProduct = function(){
var myObject = $(this);
// do something
}
// Call it like:
$("ul.products").addProduct();
This is a bit tricky though because you are making methods that are very specific to lists. So, to be sure you should at least add some checking on the object's type and handle the code correctly if the current object is, let's say an input element.
An alternative is to make a normal Javascript method that receives the list as a parameter. That way you can make a more list specific method.

I think you want to add a function to that DOM Object.
$(function(){
// [0] gets the first object in array, which is your selected element, you can also use .get(0) in jQuery
$("#test")[0].addProduct = function(info){
alert("ID: " + this.id + " - Param: " + info);
};
$("#test")[0].addProduct("productid");
});
Above script wil alert "ID: test - Param: productid"
A live example: http://jsfiddle.net/jJ65A/1/
Or normal javascript
$(function(){
document.getElementById("test").addProduct = function(info){
alert(info);
};
});

I think may be just using delegate in jQuery:
$(".parentclass").delegate("childclass","eventname",function(){});

Related

Passing correct jQuery selector to an object

I am writing a jQuery plugin which, ideally I would like in it's own namespace.
So far, this seems to work (in terms of namespace nesting)
(function($) {
$.fn.nspace = {
foo: function() {
// Does not work becuase $(this) is not the correct selector.
$(this).show();
}
}
})(jQuery);
So given then example above, I might call my function like so:
$("html, body").nspace.foo();
but $(this) is not [html, body]...How can I solve this?
EDIT: To clarify (based on user comments)...
$("html, body").nspace.foo(); should call foo for [html, body] but, $(this) inside nspace resolves to nspace...so it's trying to call nspace.foo();
You shouldn't do this, but just because I dislike when someone says "You can't" in programming (often untrue, especially in Javascript) - here's how you could do this:
The jQuery object is constructed each time using its prototype.init function, which is aliased to fn.init, so you could overwrite it with a wrapped function that adds your namespace object in a way that doesn't harm any existing usage or libraries, like so:
(function($) {
var baseInit = $.fn.init;
$.fn.init = function(selector, context, rootjQuery) {
// Instantiate jQuery the way it expects
var j = new baseInit(selector, context, rootjQuery);
// Add our extra object/namespace
// Use j inside to refer to the current jQuery object
j.nspace = {
foo: function() {
j.show();
}
};
// Return it all and other libraries are none the wiser
return j;
}
})(jQuery);
http://jsfiddle.net/b9chris/7TPZY/
You should consider using the classic pattern for a jQuery plugin: define only one method: in your case, nspace. Inside this method, you'll take every case into account. Sounds hard, but it's pretty easy once you've looked into that.
(By the way you definitely have to look at that when writing a jQuery plugin)
You can't add an object as a plugin and still get the jQuery object that was used to get the object. You simply have no reference to that jQuery object when you call a method in your object.
Put the function directly as the plugin:
(function($) {
$.fn.nspace = function() {
this.show();
};
})(jQuery);
Usage:
$("html, body").nspace();
(Note that the object is the jQuery instance, not a selector or an element, so you don't need to use $(this)).

How to make a jQuery plugin function callable for stand-alone use, that does not operate on a collection

I read the jquery documentation of plugin authoring and am familiar with that. However, the examples given always operate on a set of previously matched elements. I want to create a function that can do both:
// example usage of my to-be-created plugin function
// this is the way described in the docs, and I know how to do that
$("a").myFunction ()
// but I also want to be able to call the function without a collection:
$.myFunction ();
If $.myFunction ()is called without a collection to operate on, it would create it's own collection of what elements to match - kind of an initialization process (but not necessarily run only once). Also, $.myFunction ()should maintain chainability.
The pseudocode of what I want to achieve:
// [...]
function myFunction (): {
if (notCalledOnACollection) {
// this should run when called via $.myFunction ()
$elements = $("a.myClass");
}
else {
$elements = $(this);
}
return $elements.each (function () {
// do sth. here
});
}
I would really like to keep all of the functions implementation/functionality within a single function definition, and not have two separately named functions or two equally named functions in two separately places within the jQuery object.
And of course I could add a parameter myFunction (do_init) that indicates what branch of the if statement to execute, but that would clutter my argument list (I want to use that approach for multiple plugins, and there will be argumentes to myFunction () that I just left out here for simplicity).
Any good suggestions?
By simply adding another reference in the plugin definiton, you can easily use the standard plugin code:
(function( $ ) {
$.myPlugin = $.fn.myPlugin = function(myPluginArguments) {
if(this.jquery)
//"this" is a jquery collection, do jquery stuff with it
} else {
//"this" is not a jquery collection
}
};
$.fn.myPlugin.otherFunc = function() {
};
})( jQuery );
The only difference here is the $.myPlugin = part which allows you to directly call your plugin without running jquery's selector function. Should you decide you need other functions or properties, you can create them as properties of your plugin.
Usage:
//using a selector (arguments optional)
$(".someClass").myPlugin();
//using the options variable - or whatever your arguments are
$.myPlugin({id: "someId"});
//accessing your other functions/properties
$.myPlugin.otherFunc();

javascript: anonymous function expose functions (how frameworks really works)

i was exploring in the last few days how big frameworks works , how they assign their function name and it can't(?) be override , i pretty much know how framework work with anonymous function , for example they do it this way or similar version :
(function(){
var Sizzle = function (){
var x;
};
Sizzle.f = function(){
alert("!");
};
window.Sizzle = Sizzle;
})();
i still don't get few things about those huge frameworks and i hope i can find answer :
how do they assign function name and the name can't be override?
in the code above to call the function i need to write Sizzle.f() to get the function to work , but when i use jquery i don't write Jquery.show() , just show() , how do they vanish the "jquery" from "jquery.show()" function call?
by saying the name can't be override i mean , if i create function with one of the jquery functions names , the jquery function will work.
thanks in advance.
As has been shown for #2, it's really easy for BIG_NAMESPACE.Functions.doStuff to be added to anything you want.
var _ = BIG_NAMESPACE.Functions.doStuff;
_(); // runs BIG_NAMESPACE.Functions.doStuff;
As for #1:
Most libraries DO let their functions be overwritten.
It's the values that are inside of the framework's closure which are preserved, for safety reasons.
So you could do something like:
BIG_NAMESPACE.Functions.doStuff = function StealEverything() {};
(BIG_NAMESPACE.Functions.doStuff === StealEverything) // true;
But doStuff would have NO access to any of the variables hidden inside of the framework's closure.
It would also mean that until the page was reloaded, doStuff would also not work the way you want it to.
HOWEVER, in newer versions of JavaScript (ECMA5-compatible browsers), it WILL be possible to do something like what you're suggesting.
BIG_NAMESPACE = (function () {
var do_stuff = function () { console.log("doin' stuff"); },
functions = {
set doStuff (overwrite) { }
get doStuff () { return do_stuff; }
};
return { Functions : functions };
}());
Then, this will work:
BIG_NAMESPACE.Functions.doStuff(); // "doin' stuff"
BIG_NAMESPACE.Functions.doStuff = function () { console.log("ain't doin' jack"); };
BIG_NAMESPACE.Functions.doStuff(); // "doin' stuff"
However, Frameworks aren't going to use this for a LONG time.
This is not even remotely backwards compatible. Maybe in 2016...
There were defineGetter and defineSetter methods as well, but they aren't a formal part of the JavaScript language. Like innerHTML, they're things that the browser vendors put in, to make life better... ...as such, there's no real guarantee that they're going to be in any/all browsers your users have. Plus, they're deprecated, now that new browsers use the get and set constructs that other languages have.
(function(){
var jqueree = {};
jqueree.someval = 22;
jqueree.somefunc = function(){ alert(this.someval); };
window.jqueree = jqueree;
window.somefunc = function(){ jqueree.somefunc.call(jqueree); };
window.$$$ = jqueree;
})();
// all equivalent
window.somefunc();
window.jqueree.somefunc();
$$$.somefunc();
somefunc();
Answering your Questions
At the top of jQuery you'll see: var jQuery = (function() {, which creates the local function (its incomplete; the }); occurs elsewhere).
At the very end of jQuery you'll notice the following, which is how it attaches it to the global namespace:
// Expose jQuery to the global object
window.jQuery = window.$ = jQuery;
I have never seen a jQuery function called without referencing the jQuery object. I think you always need to use jQuery.show() or $.show(); however maybe you're saying you don't have to call window.jQuery.show(), which you are permitted to drop the window, since that is the default.
Using your example
(function(){
/* This is where Sizzle is defined locally, but not exposed globally */
var Sizzle = function (){
var x;
};
/* If you put "window.f = Sizzle.f = function(){" then you could *
* call f() w/o typing Sizzle.f() */
Sizzle.f = function(){
alert("!");
};
/* The following line is what makes it so you can use Sizzle elsewhere *
* on your page (it exposes it globally here) */
window.Sizzle = Sizzle;
})();
use function _name_() {} and the name is static
the simply use var $ = jQuery; to create an alias.
jQuery works this way:
Supposed you have this jQuery code:
$("#title").show();
You have three elements to that line.
$ is a javascript function
"#title" is an argument to that function
.show() is a method call
Here's how it works.
Javascript executes the function named $ and passed it an argument of "#title".
That function does it's business, finds the #title object in the DOM, creates a jQuery object, puts that DOM element into the array in the jQuery object and returns the jQuery object.
The Javascript execution engine then takes the return value from that function call (which is now a jQuery object) and looks for and executes the .show() method on that object.
The .show() method then looks at the array of DOM elements in the jQuery object and does the show operation for each DOM element.
In answer to your question, there is no .show() all by itself. It's a method on a jQuery object and, in this example, that jQuery object is returned from the $("#title") function call.

Is it possible to write a second non-static, selecting, priviledged function in a JQuery Plugin?

Almost all of the examples in the jQuery tutorials that I've read, usually use one major public function for their selecting plugin. When I say 'selecting' plugin, I mean one that is not simply a static function extended onto jQuery.
For example:
(function($) {
jQuery.fn.actionList = function(options) {
var opts = $.extend({}, $.fn.actionList.defaults, options);
return this.each(function(){
alert(this);
});
};
$.fn.actionList.defaults = {
listHtml: '<div>Set the list html</div>'
};
})(jQuery);
but not:
jQuery.log = function(message) {
if(window.console) {
console.debug(message);
} else {
alert(message);
}
};
This works fine for most things, but what I would like to do is be able to call a second function on the object returned from the first call.
var actionBox = $('actionBox').actionList(options);
//Many light-cycles later
actionBox.refreshData(data);
or maybe even:
$('actionBox').actionList(options);
// laaateerr
$('actionBox').actionList.refreshData(data);
I'm guessing one or both of these is not possible or, at least not advisable, but I'm only now getting into the deepest aspects of jQuery and javascript.
Could someone explain how to do this, or if it's not possible or advisable, why? and what they would do instead?
Thanks for reading!
I'm not quite sure what you're getting at, but you can call a second function on the object returned from the first function - in fact, it is very much encouraged to return a jQuery object from your plugins, and the reason why you can chain commands in jQuery.
Using your examples
var actionBox = $('actionBox').actionList(options);
//Many light-cycles later
actionBox.refreshData(data);
would work fine, so long as both .actionList() and .refreshData(data) commands both return a jQuery object.
And
$('actionBox').actionList.refreshData(data);
would need to be
$('actionBox').actionList().refreshData(data);
EDIT:
Looking at the jQuery source code,
jQuery.fn = jQuery.prototype = {
/*
Load of 'property' functions of jQuery object...
*/
}
so, adding properties (a.k.a plugins) to jQuery.fn extends the prototype of the jQuery object. When you call
$(selector, context);
a new jQuery object is returned, using the init property function of the jQuery object
jQuery = window.jQuery = window.$ = function( selector, context ) {
// The jQuery object is actually just the init constructor 'enhanced'
return new jQuery.fn.init( selector, context );
},
I think I've got a plugin that might be very useful for you. It allows you to apply any constructor/object to jQuery as it's own namespace AND you can use 'this' as you would normally with jQuery to refer to the object set. Using this[methodName] will call a method on your object, etc.
http://code.google.com/p/jquery-plugin-dev/source/browse/trunk/jquery.plugin.js
Some code samples are here:
http://groups.google.com/group/jquery-dev/browse_thread/thread/664cb89b43ccb92c/34f74665423f73c9?lnk=gst&q=structure+plugin+authoring#34f74665423f73c9
It's about halfway down the page.
I hope you find it useful!

jQuery Plugin - Keep options object separate

I created a jQuery plugin that was working great until I started testing it with more than one object on a page. The problem is that the options object passed to each new plugin object is not always the same one associated with that specific object when I access it from inside a function in the plugin. I have a feeling that I am missing something very simple, so the code might make things more clear.
Method used to create the plugin
$.fn.myPlugin = function(options) {
return this.each(function() {
var opts = $.extend({}, $.myPlugin.defaults, options);
new $.myPlugin($(this), opts);
});
}
Function that accesses the options object
$.myPlugin = function($textbox, options) {
function doSomething($textbox) {
alert(options.someProperty);
}
}
No matter what options.someProperty was when I created the plugin. The call to doSomething inside the plugin will always return the someProperty of the first options object in the first plugin object I created for example:
$textbox.focus(function() { doSomething($textbox); } );
This will always return the same someProperty even if different objects with different options objects are focused.
I hope I have made this clear enough. Let me know if you need anymore details.
You're giving the plugin a reference to the same options object for all of the elements.
Try the following:
return this.each(function() {
new $.myPlugin($(this), $.extend({ }, options));
});
This will copy the members of the options object to a new object each time. If your options object has other objects nested within it, you might need a deep copy, like this: $.extend(true, { }, options)
EDIT: You need to extend the options object inside the each method. Otherwise, you'll still have the same object for all of the elements.
Try changing
function doSomething($textbox) {
to
var doSomething = function($textbox) {
to ensure that you are creating separate doSomething methods that use separate closures. (the first version will create a single function the first time it's called, and reuse that function and its closure)

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