Window load wrapper for jQuery - javascript

jQuery(document).ready(function($){}); is a known and great way to protect the $ from causing errors.
What I'm curious about is if jQuery(window).load(function($){}); would work in the same way?
Basically, what I have now is:
jQuery(document).ready(function($){
$(window).load(function(){
// ...
});
});
This just seems unnecessary to me, any ideas about simplifying this? I need the safety of having jQuery properly mapped to $ (or whatever the correct term is) but the same timing as window.load()

I prefer this...
(function($){
$(window).load(function(){
//everything is loaded (images, scripts, etc.)
});
// and/or
$(document).ready(function(){
// the dom is in place, but everything is not necessarily loaded
});
})(jQuery);
Note: This will only work if jQuery was included before this script. I have never encountered any problems with jQuery being undefined this way. Furthermore, you will never have problems with $ being undefined, because you are passing it into your anonymous function.

You can do this:
(function($) {
$(window).load(function(){
// ...
});
})(jQuery);
The anonymous function will be executed immediately rather than waiting for DOM ready as in the code in the question. Within the function $ will be a reference to jQuery so won't clash with any other $ defined outside the anonymous function.

You can create a local parameter:
(function($) {
$(...)
})(jQuery);
This code executes an anonymous function with a parameter named $, passing jQuery as the parameter value.

Related

jQuery $ not defined - Issues using window load

I'm getting a $ not defined error in the second case below, but not the first. jQuery is installed and working on the site.
Any code using $ in here runs fine:
jQuery(function($) {
alert("Yay!");
});
Anything inside of this errors with $ not a function:
jQuery(window).load(function($) {
alert("Why not!");
});
The error is because the load() event handler does not accept a jQuery object as an argument as document.ready (which is what your first example is shorthand for) does. In the second example your $ variable is actually a reference to the Event object, as such you're probably calling methods which don't exist.
If you want to use $ to reference jQuery, then it should be available by default. If for whatever reason it isn't, for example if you're using Wordpress, then you can use jQuery.noConflict() or an IIFE to re-alias it.
It's also worth noting that load() is deprecated. To hook to the window.load event use on():
jQuery(window).on('load', function() {
// your logic here...
});

jQuery functions - re-invoking a self invoking function

I have a function that is I think is self invoked and I'm trying to figure out how to call it again.
This is how the function is declared:
jQuery(function setupFormInputHandlers(){
...
}
I try to put setupFormInputHandlers() in the developer tools console but I get an undefined error.
See jQuery document ready
// Passing a named function instead of an anonymous function.
function readyFn( jQuery ) {
// Code to run when the document is ready.
}
$( document ).ready( readyFn );
//invoke again
readyFn()
$ is just used as alias to jQuery so when you say $('x') you mean jQuery('x')..the main function is overloaded to make it familiar and to allow working with ease... also what you are asking about the function (may be you missed pasting other part)
$(function(){}); or
jQuery(function(){});
both are methods of calling anonymous function shorthand for
$(document).ready(function()
{
//your code
}
);`
in simple words it means "When the document loading complete register your an anonymous function"

different ways to execute javascript code?

I see
First
$(function() {
...
});
Second
(function() {
})();
Third
function() {
}
$(document).ready(function(){
});
Maybe there are more, what are the differences?
Your notation is mainly jQuery (atleast the ones with $)
This is shorthand for a DOM ready function, equivalent to the bottom one
This is a self executing function with the parameter specified in the trailing ()
This is a DOM ready function $(document).ready(function() {}); atleast, the function above it is simply a function.
so these indeed are a few different ways to execute javascript code, some of them are library dependent (using jQuery) others are done specifically because of differences in scope.
the first block:
$(function() {
...
});
is utilizing the js library jQuery that uses the namespace '$' what you are doing here is calling the jQuery '$' function passing in the first parameter of another anonymous function... this is a shorthand way to call $(document).ready(function(){});... both of those statements wait for the DOM to complete loading (via the onload event) before interpreting the javascript inside
the second block:
(function() {
})();
is a procedure called an (IIFE) Immediately-Invoked Function Expression... which in essense is defining an anonymous function and calling it immediately.
the third block:
function() {
}
$(document).ready(function(){
});
represents two things... the first function declared actually should have been named something like function myFunction(){...} and thus could be called later myFunction(parameters);
and finally $(document).ready(function(){}); is the javascript library jQuery's way of saying grab the 'document' element of the dom, and attach an event listen to it looking for the onload event, when that event is triggered execution the function passed as a parameter...

Pass Jquery alias into javascript function

Im creating a theme for wordpress and I need to use some jQuery. Ive found bits of code online and ive made a few bits myself. However, when using jQuery provided by wordpress it is in noConflict mode and instead of using $ it is set to "jQuery". That is fine but I dont want to have to modify all my code and any code I find online to use "jQuery" instead of $.
So it tells me that by placeing function ($) at the end you are able to use the $ as the jQuery alias, but only in that functions scope. That is fine, but I was hoping that it would work and pass through to the functions I call from inside that scope. That is where my problem is. How can I make the jQuery code that uses $ inside my "resizeandcenter" function work.
jQuery('.artworklist > li > a > img').load(function ($){
resizeitems('artworklist');
});
This is my function that I want to be able to use the $ inside as I dont want to have to modify all my code / and any code I find online.
function resizeitems(elementname){
//Do some jquery stuff using $
}
Perhaps there is an alternative way to do what I am doing or I am doing it wrong?
EDIT:
My function "resizeitems" is on its own in a js file thats included in my page header.
The other code, the jQuery code in my first code block is at the bottom of the page in a script block.
So im a bit unsure about the answer saying to wrap my function?
You can wrap your entire code in a self executing closure (or an on ready/load closure) like this
(function ($) {
// do your stuff here
}(jQuery));
Then you can use $ within that closure
Here is an example on jsfiddle for you
window.addEventListener("load", function () {
(function ($jq) {
$jq("body").append($jq("<div>").text("hello"));
}(jQuery));
}, false);
Here is an example using jquery's ready event listener
jQuery(document).ready(function() {
(function ($jq) {
$jq("body").append($jq("<div>").text("hello"));
}(jQuery));
});
On jsfiddle
Or a further alternative in jquery, mostly syntax change, as suggested by #Mathletics
jQuery(function($jq) {
$jq("body").append($jq("<div>").text("hello"));
});
On jsfiddle
You need to pass jQuery into the top-level closure containing your code. Usually this is inside the $(document).ready() call. A basic example looks like this:
jQuery(function($) {
function resizeitems(elementname){
//Do some jquery stuff using $
}
$('.artworklist > li > a > img').load(function (){
resizeitems('artworklist');
});
});
jQuery is now aliased to $ inside of that closure.
All what matter is scope here. If your other functions are in some other scope you can just remap global jQuery to $ in that scope, so that you don't have to change the code.
var $ = jQuery;
You can even set it in global scope, but you may affect other usage of $ on the page if it was used for something else:
window.$ = jQuery;

Do self executing functions run at dom ready?

Before I heard about self executing functions I always used to do this:
$(document).ready(function() {
doSomething();
});
function doSomething()
{
// blah
}
Would a self executing function have the same effect? will it run on dom ready?
(function doSomething($) {
// blah
})(jQuery);
Nope. A self executing function runs when the Javascript engine finds it.
However, if you put all of you code at the end of your document before the closing </body> tag (which is highly recommended), then you don't have to wait for DOM ready, as you're past that automatically.
If all you want is to scope your $ variable, and you don't want to move your code to the bottom of the page, you can use this:
jQuery(function($){
// The "$" variable is now scoped in here
// and will not be affected by any code
// overriding it outside of this function
});
It won't, it will be ran as soon as the JavaScript file is executed.
No, self-executing javascript functions run right there.
If you want to create a DOM ready function, write the following:
$(function() {
// this will run on DOM ready
});
Which is a shorthand of:
$(document).ready(function() {
});
No, the self-executing function run immediatly after you "declare" it on your code. Even if it's located on an external .js file.
In your example, there is a possibility that your function will execute and the value of jQuery is undefined. If you want your code to be executed on DOMReady, continue using
$(document).ready(function(){
doSomething();
});
or
$(function(){
doSomething();
});
or even
window.onload = function(){
doSomething();
}
$(document).ready(function() { ... }); simply binds that function to the ready event of the document, so, as you said, when the document loads, the event triggers.
(function($) { ... })(jQuery);
is actually a construct of Javascript, and all that piece of code does is pass the jQuery object into function($) as a parameter and runs the function, so inside that function, $ always refers to the jQuery object. This can help resolve namespacing conflicts, etc.
So #1 is executed when the document is loaded, while #2 is run immediately, with the jQuery object named $ as shorthand
$(document).ready(function(){ ... }); or short $(function(){...});
This Function is called when the DOM is ready which means, you can start to query elements for instance. .ready() will use different ways on different browsers to make sure that the DOM really IS ready.
(function(){ ... })();
That is nothing else than a function that invokes itself as soon as possible when the browser is interpreting your ecma-/javascript. Therefor, its very unlikely that you can successfully act on DOM elements here.
jQuery document.ready vs self calling anonymous function

Categories

Resources