Why does jQuery.ready run when the page isnt ready? - javascript

so often i put jquery document ready functions at the bottom of my html, just to have it run before all the elements of the page are loaded. i'm tired of my functions not working because resources arent finished loading on the page, jquery.ready keeps saying the elements are done loading when they arent! who wants to set a 300ms timeout just so that their functions wait a little after jquery.ready?

Use .ready() to perform actions when the DOM is ready for scripting.
$(document).ready(function(){
});
Use .load() to perform actions when the "page" (resources including files and images) is loaded.
$(window).load(function(){
});

jQuery.ready fires when DOM elements are ready, not when scripts/images/etc finish loading.
Description from the docs on .ready():
Specify a function to execute when the DOM is fully loaded.

As simshaun said, jQuery.ready fires when the DOM is ready - not when things like images are ready. If you want to wait for images to be loaded, you have to use the following code:
$(window).load(
function() {
// do stuff here
}
);

$.ready runs when DOM is loaded not when the page is fully loaded (images etc...)
Perhaps you're looking for
$(window).load(function() {
// stuff
});

From the jQuery API documentation:
While JavaScript provides the load event for executing code when a page is rendered, this event does not get triggered until all assets such as images have been completely received. In most cases, the script can be run as soon as the DOM hierarchy has been fully constructed. The handler passed to .ready() is guaranteed to be executed after the DOM is ready, so this is usually the best place to attach all other event handlers and run other jQuery code. When using scripts that rely on the value of CSS style properties, it's important to reference external stylesheets or embed style elements before referencing the scripts.
So, use the load event if you need everything to be finished loading but if you only need the DOM to be ready, use the ready event.

.ready() function runs when the DOM is ready not the binary data is loaded. to ensure that the binary data is loaded you can use .load() function

Related

JavaScript function after page load and other JS/Ajax function completion [duplicate]

I was using $(window).load(function(){}); for my projects until somewhere I saw that somebody said we could just use $(function(){}); and they would perform identically.
But now that I have more experience I have noticed that they are not identical. I noticed that the first piece kicks in a little bit after the second piece of code.
I just want to know what's the difference?
$(document).ready(function(){})
will wait till the document is loaded(DOM tree is loaded) and not till the entire window is loaded. for example It will not wait for the images,css or javascript to be fully loaded . Once the DOM is loaded with all the HTML components and event handlers the document is ready to be processed and then the $(document).ready() will complete
$(window).load(function(){});
This waits for the entire window to be loaded. When the entire page is loaded then only the $(window).load() is completed. Hence obviously $(document).ready(function(){}) finishes before $(window).load() because populating the components(like images,css) takes more time then just loading the DOM tree.
So $(function(){}); cannot be used as a replacement for $(window).load(function(){});
From the jQuery docs itself.
The first thing that most Javascript programmers end up doing is adding some code to their program, similar to this:
window.onload = function(){ alert("welcome"); }
Inside of which is the code that you want to run right when the page is loaded. Problematically, however, the Javascript code isn't run until all images are finished downloading (this includes banner ads). The reason for using window.onload in the first place is that the HTML 'document' isn't finished loading yet, when you first try to run your code.
To circumvent both problems, jQuery has a simple statement that checks the document and waits until it's ready to be manipulated, known as the ready event:
$(document).ready(function(){
// Your code here
});
Now,
$(window).load(function(){}); is equal to window.onload = function(){ alert("welcome"); }
And, $(function(){}); is a shortcut to $(document).ready(function(){ });
I think , this clears everything :)
$(window).load from my experience waits until everything including images is loaded before running where as $(function() {}); has the same behaviour as $(document).ready(function() {});
Please someone correct me if I am wrong.
The second is/was a shortcut for $(document).ready(), which should run before window's load event.
Note that $(document).ready() is the preferred way of binding something to document load; there are a couple other ways of doing it like the one you showed, but that's preferred.

hiding container until fully loaded not working with cached images

I have a website with a background and a main container. I wanted to hide the container until the whole page has been loaded. so i added
#cover{opacity:0}
at the start of the page and
$(window).load(function() {
$('#cover').css('opacity','1');
});
at the end, just before </body> tag. It works perfectly when page is loaded for the first time.
PROBLEM : If I load the same page once more, it shows all the images and text scattered throughout the page. It works fine once completely loaded. certainly this type of behavior is caused by cached images. but all the images are inside the main container which has opacity:0, This has completely confused me.
UPDATE 1:
I am using turn.js to convert the whole container into a book, i want the book become visible when the book is ready i.e. both loading of images and javascript initialization has completed.
UPDATE 2:
This is how i am checking for "images loaded" and "javascript initialized". it worked as i wanted it to. is this a good way to handle the situation?
$(window).load(function(){
$(window).ready(function() {
$('#cover').css('opacity','1');
});
});
$(window).ready(function(){
$(window).load(function() {
$('#cover').css('opacity','1');
});
});
The problem may be related to your $('window').onload();
Take some time and read this SO post.
what-is-the-difference-between-window-load-and-document-ready
load is called when all assets are done loading, including images.
ready is fired when the DOM is ready for interaction.
From the MDC, window.onload:
The load event fires at the end of the document loading process. At
this point, all of the objects in the document are in the DOM, and all
the images and sub-frames have finished loading.
From the jQuery API
documentation, .ready( handler ):
While JavaScript provides the load event for executing code when a
page is rendered, this event does not get triggered until all assets
such as images have been completely received. In most cases, the
script can be run as soon as the DOM hierarchy has been fully
constructed. The handler passed to .ready() is guaranteed to be
executed after the DOM is ready, so this is usually the best place to
attach all other event handlers and run other jQuery code. When using
scripts that rely on the value of CSS style properties, it's important
to reference external stylesheets or embed style elements before
referencing the scripts.
Let me know if this change works.
You do not call the same block in your CSS (#container) and in your JS (#cover).

Are all CSS applied in document.load?

I'm trying to create function which will invoke after every part of the document is loaded and applied.
So: are all css applied in document.load? Does document.load invoke if some resources will have 404 error?
The load event will fire after the entire, initial document (including dependancies), as described by the HTML (and CSS) source, has loaded.
Content added to the DOM with JavaScript may not finish loading until after the load event had fired.

what is the best way to make sure javascript is running when page is fully loaded?

I am trying to run my javascript in my asp.net webform page but I am not sure it runs properly because all the elements are not loaded yet. How can I make sure my script is at the very bottom of the page with using jquery? So it can run when the page is loaded?
Even though everyone says use $(document).ready it's kind of an anti-pattern.
What you really want to do is put any scripts you want to load at the end of the body
<html>
<head> ... </head>
<body>
...
<script src="..." ></script>
</html>
As long as your scripts are at the end of all your other HTML content the javascript will only fire when the content above it has loaded.
With pure JavaScript, you can use
window.onload = function() {
// Page loaded
};
Or you can use jQuery's ready function:
$( document ).ready( function() {
// Dom loaded
} );
Note: jQuery's ready function fires when the DOM has loaded (unless the browser does not support a dom-ready method), not when the whole page has loaded (images, scripts, etc).
Use .ready():
$(document).ready(function($) {
// page is loaded
});
While JavaScript provides the load event for executing code when a
page is rendered, this event does not get triggered until all assets
such as images have been completely received. In most cases, the
script can be run as soon as the DOM hierarchy has been fully
constructed. The handler passed to .ready() is guaranteed to be
executed after the DOM is ready, so this is usually the best place to
attach all other event handlers and run other jQuery code. When using
scripts that rely on the value of CSS style properties, it's important
to reference external stylesheets or embed style elements before
referencing the scripts.
With jQuery, you want to attach to the ready event. This gets fired when all DOM elements have been loaded:
jQuery(document).ready(function(){
// jQuery Code here
});
Shorthand version:
$(function(){
// ...
});
Using this method, I usually put my jQuery in an external file, or in the <head> tag.
You should put your code inside the document ready block as suggested in the JQuery documentation.
This way it will be loaded when all the scripts will be loaded.
$(document).ready(function(){
//Put your code here
});
What is the best way to make sure javascript is running when page is fully loaded?
If you mean "fully loaded" literally, i.e., all images and other resources downloaded, then you have to use an onload handler, e.g.:
window.onload = function() {
// Everything has loaded, so put your code here
};
If you mean "after all of the HTML has been parsed and all elements are accessible from script", at which point images may still be downloading, then you can either put your script at the bottom of the source HTML or use a document.ready handler. Or both. Refer to any of the other answers for details.

What event does JQuery $function() fire on?

We have a JQuery $(function() statement as:
<script type="text/javascript">
$(function(){
//Code..
})
</script>
Dumb question - when exactly is this function executed? Is it when the entire HTML page has been downloaded by the client?
What is benefit of using the wrapping your code within $(function() as opposed to just doing:
<script type="text/javascript">
//Code..
</script>
It fires when the document has been parsed and is ready, and is the equivalent of $(document).ready(function () { }).
The obvious benefit is that having your script tag before other elements on the page means that your script can interact with them even though they're not available at parse time. If you run your script before elements have been parsed and the document is not ready, they will not be available for interaction.
It is executed as soon as the DOM is parsed and is invoked in order of appearance if there are multiple appearances. At this point the document is however not displayed, its just parsed.
When the document completes loading. It is the same as writing this:
$(document).ready(function(){});
EDIT: To answer your second question:
If you don't wrap your code in the block above then it would fire as soon as it is encountered instead of after all the controls on the page have loaded. So if a block was at the top of a page and it referred to elements in the page those references would not work as the elements have not loaded yet.
But if you wrap in the block then you know that the page has loaded and all elements are available to now reference.
It fires after the the document has fully loaded, the DOM tree has been initialized, all CSS styles have been applied and all Javascript has been executed. It differs from the load event in that elements (other than CSS/JS) that load their content from other URLs, such as images or flash files, have not necessarily finished loading at this point. This is usually called the "domready" or "domloaded" event, and some modern browsers support it directly (e.g. Firefox has a DomContentLoaded event), and on others it can be simulated with various tricks, like using the defer attribute or placing a script at the very end of the body.
The advantage is that you can reliably interact with the document at this time; for example you can set an event handler on an element with a certain ID and be sure that it already exists in the DOM tree. On the other hand, it can run considerably earlier than the load event, if some external resource is slow to load. If your script is at the end of your HTML code, then there might be little difference in using or not using the domready event, but usually scripts are called from the head tag, and at that point no elements of the body are available yet.

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