In jQuery is it possible to set a method as a var? - javascript

Let's say I have a lot of instances of $(this).show("slow", function(){fVar;}); where $(this) are different objects at different times, but they all need .show("slow", function(){fVar;}); and fVar is a previously defined function var.
Is it possible to set .show("slow", function(){fVar;}); as a var like "myVar" so I could theoretically do something like $(this).myVar();

You sure can. Check out the jquery docs
(function( $ ) {
$.fn.myPlugin = function() {
// Do your awesome plugin stuff here
};
})( jQuery );
don't forget about proper namespacing! And just use the method that you declare (so mPlugin) just as you would any other JQuery method

I'm not so much into JQuery but try this -
$.prototype.myVar=function(){
//here goes your code
}

just create it as a function expression and you can use it wherever you want. this function takes in an event object that is created by an event listener. ie: click functions. use this var as your event function callback and pass in the event object so it knows what to show.
var showSlow = function(eventObject){
$(eventObject).show("slow", function(){
fVar;
});
}

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)).

Is it possible to preserve 'this' when calling a function in javascript via an anonymous function?

Let's say I have a jquery plugin that has an onSelect attribute. The user sets it to a function, and when that function is called, this refers to the object the plugin is applied to. All is good.
If I want to write a plugin that wraps this plugin, in order to inject some code into the onSelect, I do something like this:
// Get whatever the user put in
var extOnSelect = options['onSelect'];
// delete the onSelect attribute
delete options['onSelect'];
// re-add onSelect as an anonymous function that calls my method and the user's
var options = $.extend({
'onSelect': function() { onSelect(); extOnSelect(); }
}, options);
// call the plugin that I am wrapping / injecting extra onSelect code into
$(this).externalPlugin(options);
Then it will pass in my own onSelect code, while preserving what the user entered.
The only problem is, within each of those two functions this no longer refers to the object, it now refers to I think the generic inline function.
What's the best solution to fix this?
Use apply and the arguments object:
extOnSelect.apply(this, arguments);
to call extOnSelect exactly like the current function.
You could use call, but then you would need to pass the event object (and other possibe arguments) explicitly.
I think you need to use call method of javascript functions.
var options = $.extend({
'onSelect': function() { onSelect.call(this); extOnSelect.call(this); }
}, options);

In JavaScript is it possible to add to a callback function instead of overwriting it?

I don't know if I'm saying this right, so I'll just ask by explaining with an example.
Let's say I've written a jQuery plugin with an onShowEdit callback.
I later use my plugin and add a bunch of other default functions/methods to the event:
$('.editable_module:not(.custom)').editable({
onShowEdit: function(el){
initRequired();
$(':radio, :checkbox', el).prettyCheckboxes();
initDatePickers();
initChosen();
initMaskedInputs();
$('.dynamic_box.tabs').dynamicBoxTabs();
$('.trigger_dynamic_box').triggerDynamicBox('true');
}
});
So now I have a basic/default element (.editable_module) that calls the plugin and has some methods/functions that are going to be used in all instances.
My question comes when I have a need to add something to this for a 'one time' kind of deal (I need to add some behavior to this callback/event but not something that is used normally). Is it possible to extend or add to this callback/event without overwriting it? I mean, I know I can go in and do this:
$('#new_selector').editable({
onShowEdit: function(el){
initRequired();
$(':radio, :checkbox', el).prettyCheckboxes();
initDatePickers();
initChosen();
initMaskedInputs();
$('.dynamic_box.tabs').dynamicBoxTabs();
$('.trigger_dynamic_box').triggerDynamicBox('true');
//ADD SOME NEW STUFF HERE
}
});
But is that really my only option?
Thanks in advance for any input/suggestions.
You could consider jQuery's own event system as follows: http://jsfiddle.net/VQqXM/1/. You can integrate this in your $.fn function pretty easily - just pass the appropriate function as property of the object instead of a function literal.
$("input").on("foo", function() {
alert(1);
});
// later
$("input").on("foo", function() {
alert(2);
});
// later
$("input").trigger("foo"); // alerts 1 and 2
You can simply use .on/.off to bind and unbind events, and trigger them all with .trigger. jQuery also supports namespacing of the event names to make sure you're not using an already used event.
You could use the new $.Callbacks() method
var $onShowEditCBObj = $.Callbacks();
function onShowEditHandler() {
$onShowEditCBObj.fire();
}
$('#new_selector').editable({
onShowEdit: onShowEditHandler
});
// add default event to callbacks obj
$onShowEditCBObj.add(function(){
initRequired();
$(':radio, :checkbox', el).prettyCheckboxes();
initDatePickers();
initChosen();
initMaskedInputs();
$('.dynamic_box.tabs').dynamicBoxTabs();
$('.trigger_dynamic_box').triggerDynamicBox('true');
});
// add a one time method to the callbacks obj
function oneTimeEvent () {
alert("worky");
$onShowEditCBObj.remove(oneTimeEvent);
}
$onShowEditCBObj.add(oneTimeEvent)
With this setup, you can change what callbacks will be fired without having to do anything extra to the editable plugin.
Edit: I didn't realize that you wrote the plugin. With that in mind, pimvdb's answer is more robust than requiring the developer to code a certain way.
If I understand the question correctly, the key word here is "factory".
jQuery is itself a factory but to get what you describe, you need your plugin also to be a factory within the factory. That requires the plugin to be written in a certain way.
Probably the easiest approach is to use jQuery's UI widget factory. Read about it here.
Defining a separate function for onShowEdit should work.
var myOnShowEdit = function(el, extra_fn) {
//standard functionality goes here
if (typeof extra_fn==='function') extra_fn(); //support for extra stuff
}
$('.editable_module:not(.custom)').editable({
onShowEdit: function(el) {
myOnShowEdit(el);
}
});
$('#new_selector').editable({
onShowEdit: function(el) {
myOnShowEdit(el, function(){console.log('hi');});
}
});
This will give you fair flexibility to add whatever functionality you need in addition to the standard stuff. Just be aware of how this may shift contexts.

Make variables from jquery function to be accessible from other functions

I have a jquery function like this:
(function($){
$.fn.myjqfunction = function(cfg){
var foo1, foo2;
return this.each...
};
})(jQuery);
How can I make foo1 and foo2 to be accessible from outside (from another function like this)?
These variables will store the state of some things that affect the entire document, and I want the other function to be aware of that...
Declare them outside the function, i.e., global.
You may want to put them in a namespace/object/module to be on the safe side. Which method is best depends on what you're actually doing with them.
For example, if they're related to specific selectors, it might be "best" to attach them directly to the DOM elements using .data, or keep them inside another jQuery function, etc.
Set up your function like this:
(function($){
function myjqfunction( cfg ) {
return this.each( ... );
}
$.myjqfunction = {
foo1: ... ,
foo2: ...
};
$.fn.myjqfunction = myjqfunction;
})(jQuery);
Then from outside your plugin, code can refer to $.myjqfunction.foo1 to get at those variables, and you'd refer to them the same way from inside your plugin code.
There are of course other similar ways to set that up.

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.

Categories