If I have some code like this:
jQuery(document).ready(function() {
jQuery('body').on('mouseup', '.some-div', function(e){
});
});
Is it possible to trigger the mouseup event outside the (document).ready()
with
jQuery('.some-div').mouseup();
or should I write this code
jQuery('body').on('mouseup', '.some-div', function(e){
});
as a function outside the (document).ready()?
I don't think dependency matters as much as loading order of the whole file. $(document).ready ensures that jQuery waits to execute the main function until
the page Document Object Model (DOM) is ready for JavaScript code to
execute.
Code outside this ready block might (be tried to) run before the page is actually ready. For instance, let's say this is code that's in the head of your page:
<script>
jQuery(document).ready(function() {
jQuery('body').on('mouseup', '.some-div', function(e){
});
});
jQuery('.some-div').mouseup();
</script>
The ready block will wait, as described above, but the mouseup trigger will try to fire, but it can't. The DOM isn't ready yet, which means .some-div can't be found yet - and thus, the trigger can't be activated.
To improve the chances that DOM is ready, you can try to load your jQuery before the closing </body> tag. The ready block can stay in the head, but the trigger should then move to the end of the document to improve the likelihood that the DOM is ready (which it normally should at that stage). For an interesting read on where to place script tags, also see this highly popular post.
jQuery('.some-div').mouseup(callback); writing this outside of document ready does not ensure document is ready before event is being attached to a document element. It may happen jQuery('.some-div') is not there before we are trying to access and attach an event listener.
jQuery(function() {
jQuery('body').on('mouseup', '.some-div', function(e){
});
is equivalent to
jQuery(document).ready(function() {
jQuery('body').on('mouseup', '.some-div', function(e){
});
});
Both the ways are good to ensure availability of dom elements before access.
Once the event is attached you can trigger any time. But you should always make sure document is ready.
Once .ready() is executed and event is binded, you can call it outside of that function.
Yes it's possible to trigger mouseup outside $.ready() using
jQuery('.some-div').mouseup();
But remember to call it after $.ready gets executed. In practice it requires another $.ready handler or just the invocation in the same one at the end.
Try this :
$(document).on('mouseup','.some-div',function(){
//code there
});
Related
What are differences between
$(document).ready(function(){
//my code here
});
and
$(window).load(function(){
//my code here
});
And I want to make sure that:
$(document).ready(function(){
})
and
$(function(){
});
and
jQuery(document).ready(function(){
});
are the same.
Can you tell me what differences and similarities between them?
$(document).ready(function() {
// executes when HTML-Document is loaded and DOM is ready
console.log("document is ready");
});
$(window).load(function() {
// executes when complete page is fully loaded, including all frames, objects and images
console.log("window is loaded");
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
Query 3.0 version
Breaking change: .load(), .unload(), and .error() removed
These methods are shortcuts for event operations, but had several API
limitations. The event .load() method conflicted with the ajax .load()
method. The .error() method could not be used with window.onerror
because of the way the DOM method is defined. If you need to attach
events by these names, use the .on() method, e.g. change
$("img").load(fn) to $(img).on("load", fn).1
$(window).load(function() {});
Should be changed to
$(window).on('load', function (e) {})
These are all equivalent:
$(function(){
});
jQuery(document).ready(function(){
});
$(document).ready(function(){
});
$(document).on('ready', function(){
})
document.ready is a jQuery event, it runs when the DOM is ready, e.g. all elements are there to be found/used, but not necessarily all the content.
window.onload fires later (or at the same time in the worst/failing cases) when images and such are loaded. So, if you're using image dimensions for example, you often want to use this instead.
Also read a related question:
Difference between $(window).load() and $(document).ready() functions
These three functions are the same:
$(document).ready(function(){
})
and
$(function(){
});
and
jQuery(document).ready(function(){
});
here $ is used for define jQuery like $ = jQuery.
Now difference is that
$(document).ready is jQuery event that is fired when DOM is loaded, so it’s fired when the document structure is ready.
$(window).load event is fired after whole content is loaded like page contain images,css etc.
From the jQuery API Document
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.
In cases where code relies on loaded assets (for example, if the
dimensions of an image are required), the code should be placed in a
handler for the load event instead.
Answer to the second question -
No, they are identical as long as you are not using jQuery in no conflict mode.
The Difference between $(document).ready() and $(window).load() functions is that the code included inside $(window).load() will run once the entire page(images, iframes, stylesheets,etc) are loaded whereas the document ready event fires before all images,iframes etc. are loaded, but after the whole DOM itself is ready.
$(document).ready(function(){
})
and
$(function(){
});
and
jQuery(document).ready(function(){
});
There are not difference between the above 3 codes.
They are equivalent,but you may face conflict if any other JavaScript Frameworks uses the same dollar symbol $ as a shortcut name.
jQuery.noConflict();
jQuery.ready(function($){
//Code using $ as alias to jQuery
});
$(document).ready(function(e) {
// executes when HTML-Document is loaded and DOM is ready
console.log("page is loading now");
});
$(document).load(function(e) {
//when html page complete loaded
console.log("completely loaded");
});
The ready event is always execute at the only html page is loaded to the browser and the functions are executed....
But the load event is executed at the time of all the page contents are loaded to the browser for the page.....
we can use $ or jQuery when we use the noconflict() method in jquery scripts...
$(window).load is an event that fires when the DOM and all the content (everything) on the page is fully loaded like CSS, images and frames. One best example is if we want to get the actual image size or to get the details of anything we use it.
$(document).ready() indicates that code in it need to be executed once the DOM got loaded and ready to be manipulated by script. It won't wait for the images to load for executing the jQuery script.
<script type = "text/javascript">
//$(window).load was deprecated in 1.8, and removed in jquery 3.0
// $(window).load(function() {
// alert("$(window).load fired");
// });
$(document).ready(function() {
alert("$(document).ready fired");
});
</script>
$(window).load fired after the $(document).ready().
$(document).ready(function(){
})
//and
$(function(){
});
//and
jQuery(document).ready(function(){
});
Above 3 are same, $ is the alias name of jQuery, you may face conflict if any other JavaScript Frameworks uses the same dollar symbol $. If u face conflict jQuery team provide a solution no-conflict read more.
$(window).load was deprecated in 1.8, and removed in jquery 3.0
What is the difference between
$(function()
{
$(".some").click(function()
{
...
});
});
and
$(".some").click(function()
{
...
});
I know from here that $(function() is shorthand for $(document).ready(function(). But why are we waiting for the document to be ready? Will the function not be only called when some is clicked anyway?
Note: #2 does not work in my case.
The difference is that #1 waits for the DOM to fully load before running the JavaScript.
The second code runs the JavaScript when it receives it which means it looks for .class elements before they have finished loading. This is why it doesn't work.
You need the document to be ready, i.e. all elements of the document to be available, before you can add an event listener to an element.
The reason is: consider a button, and you want an event listener (listening for the click event, for example.
When your sript runs but the button is not yet present, the attempt to attach the listener will fail. As a result, the associated function cannot be called once the button is actually clicked.
Does that answer your question?
You use the $(function()) simply because you need the DOM to fully load.
For example you have a button and you want to add some action on click. You click the button, but nothing happened, because the button was handled prior to the DOM loading.
If you won't check that the DOM is fully loaded, some unexpected behavior might occur.
Please do not confuse between onload() to ready(), as on load executes once the page is loaded and ready() executes only when the DOCUMENT is fully ready.
$(function(){...}) triggers the function when the DOM is load, it's similar to window.onload but part of jquery lib.
you can also use $(NAMEOFFUNCTION);
It's there to be sure the event has a element to listen to.
What is the difference between writing code with and without $(document).ready?
For example:
$(document).ready(function() {
$("#button").click(function() {
//Code
});
});
And:
$("#button").click(function() {
//Code
});
And :
<input id="button" type="button" value="Cancel" onclick="hidedropdown()" />
function hidedropdown() {
//Code
}
In the first case, the code isn't executed until the DOM is ready.
See documentation :
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.
If you execute the second code in a script element located at the start of your HTML or in the header, the button elements wouldn't be found and no event handler would be bound. Using .ready fixes that.
Putting your scripts at the bottom of the page (adjacent to </body>) also solves this problem for the same reason - by the time the script is parsed, the HTML will be converted to the DOM and you can traverse it.
I am a little confused with document.ready in jQuery.
When do you define javascript functions inside of
$(document).ready() and when do you not?
Is it safe enough just to put all javascript code inside of $(document).ready()?
What happens when you don't do this?
For example, I use the usual jQuery selectors which do something when you click on stuff. If you don't wrap these with document.ready what is the harm?
Is it only going to cause problems if someone clicks on the element in the split second before the page has loaded? Or can it cause other problems?
When do you define javascript functions inside of $(document).ready() and when do you not?
If the functions should be globally accessible (which might indicate bad design of your application), then you have to define them outside the ready handler.
Is it safe enough just to put all javascript code inside of $(document).ready()?
See above.
What happens when you don't do this?
Depends on what your JavaScript code is doing and where it is located. It the worst case you will get runtime errors because you are trying to access DOM elements before they exist. This would happend if your code is located in the head and you are not only defining functions but already trying to access DOM elements.
For example, I use the usual jQuery selectors which do something when you click on stuff. If you don't wrap these with document.ready what is the harm?
There is no "harm" per se. It would just not work if the the script is located in the head, because the DOM elements don't exist yet. That means, jQuery cannot find and bind the handler to them.
But if you place the script just before the closing body tag, then the DOM elements will exist.
To be on the safe side, whenever you want to access DOM elements, place these calls in the ready event handler or into functions which are called only after the DOM is loaded.
As the jQuery tutorial (you should read it) already states:
As almost everything we do when using jQuery reads or manipulates the document object model (DOM), we need to make sure that we start adding events etc. as soon as the DOM is ready.
To do this, we register a ready event for the document.
$(document).ready(function() {
// do stuff when DOM is ready
});
To give a more complete example:
<html>
<head>
<!-- Assuming jQuery is loaded -->
<script>
function foo() {
// OK - because it is inside a function which is called
// at some time after the DOM was loaded
alert($('#answer').html());
}
$(function() {
// OK - because this is executed once the DOM is loaded
$('button').click(foo);
});
// OK - no DOM access/manipulation
alert('Just a random alert ' + Math.random());
// NOT OK - the element with ID `foo` does not exist yet
$('#answer').html('42');
</script>
</head>
<body>
<div id="question">The answer to life, the universe and everything</div>
<div id="answer"></div>
<button>Show the answer</button>
<script>
// OK - the element with ID `foo` does exist
$('#answer').html('42');
</script>
</body>
</html>
The document.ready handler is triggered when the DOM has been loaded by the browser and ready to be manipulated.
Whether you should use it or not will depend on where you are putting your custom scripts. If you put them at the end of the document, just before the closing </body> tag you don't need to use document.ready because by the time your script executes the DOM will already be loaded and you will be able to manipulate it.
If on the other hand you put your script in the <head> section of the document you should use document.ready to ensure that the DOM is fully loaded before attempting to modify it or attach event handlers to various elements. If you don't do this and you attempt to attach for example a .click event handler to a button, this event will never be triggered because at the moment your script ran, the jQuery selector that you used to find the button didn't return any elements and you didn't successfully attach the handler.
You put code inside of $(document).ready when you need that code to wait for the DOM to load before executing. If the code doesn't require the DOM to load first to exist, then you can put it outside of the $(document).ready.
Incidentally, $(function() { }) is short-hand for $(document).ready();
$(function() {
//stuff here will wait for the DOM to load
$('#something').text('foo'); //should be okay
});
//stuff here will execute immediately.
/* this will likely break */
$('#something').text('weee!');
If you have your scripts at the end of the document, you dont need document.ready.
example: There is a button and on click of it, you need to show an alert.
You can put the bind the click event to button in document.ready.
You can write your jquery script at the end of the document or once the element is loaded in the markup.
Writing everything in document.ready event will make your page slug.
There is no harm not adding event handlers in ready() if you are calling your js functions in the href attribute. If you're adding them with jQuery then you must ensure the objects these handlers refer to are loaded, and this code must come after the document is deemed ready(). This doesn't mean they have to be in the ready() call however, you can call them in functions that are called inside ready() themselves.
I'm using some external jQuery with $(document).ready() to insert adverts after the document ready event has fired, something like:
$(document).ready( function() {
$('#leaderboard').html("<strong>ad code</strong>");
});
This is to prevent the UI being blocked by the slow loading of the adverts. So far it's been working well.
Now I need to insert some more ads though our CMS system, this can't be part of the external JS file, so I'm wondering can I use a second document ready event and insert it using an inline script tag? If so, what will be the order of execution the external JS document ready event first or the inline script?
You can use as many event methods as you want, jquery joins them in a queue. Order of method call is same as definition order - last added is last called.
A useful thing may be also that, you can load html code with script using ajax and when code is loaded into DOM $().ready() also will be called, so you can load ads dynamically.
Yes, adding multiple $(documents).ready()s is not a problem. All will be executed on the ready event.
Note however that your code sample is wrong. $(document).ready() takes a function, not an expression. So you should feed it a function like this:
$(document).ready( function() {
$('#leaderboard').html("<strong>ad code</strong>");
});
That function will be executed when the document is ready.
Here's a little tutorial on Multiple Document Ready
An added bonus of the jQuery way is
that you can have multiple ready()
definitions. This is the case with all
jQuery events.
$(document).ready(function () {
alert("Number One"); });
$(document).ready(function () {
alert("Number Two");
JQuery calls the ready functions in the order they are defined.
If you want to load some data first and deleay execution use holdReady().