Is this:
var contents = document.getElementById('contents');
The same as this:
var contents = $('#contents');
Given that jQuery is loaded?
Is this:
var contents = document.getElementById('contents');
The same as this:
var contents = $('#contents');
Given that jQuery is loaded?
Not exactly!!
document.getElementById('contents'); //returns a HTML DOM Object
var contents = $('#contents'); //returns a jQuery Object
In jQuery, to get the same result as document.getElementById
, you can access the jQuery Object and get the first element in the object (Remember JavaScript objects act similar to associative arrays).
var contents = $('#contents')[0]; //returns a HTML DOM Object
document.getElementBy
doesn't work correctly in <IE8. It also gets elements by name
therefore you could theoretically argue document.getElementById
is not only misleading, but can return incorrect values. I think @John new this, but I thought it wouldn't hurt to add it in. –
Storey $('#'+id)[0]
is not equal to document.getElementById(id)
because id
may contain characters which are treated special in jQuery! –
Heathenry jquery equivalent of document.getelementbyid
and the first result is this post. thank you!!! –
Disprize $('#contents')[0].id
returns id name. –
Rondure No.
Calling document.getElementById('id')
will return a raw DOM object.
Calling $('#id')
will return a jQuery object that wraps the DOM object and provides jQuery methods.
Thus, you can only call jQuery methods like css()
or animate()
on the $()
call.
You can also write $(document.getElementById('id'))
, which will return a jQuery object and is equivalent to $('#id')
.
You can get the underlying DOM object from a jQuery object by writing $('#id')[0]
.
In one sentence, DOM objects are the objects that the web browser is using to render elements on the web page whereas jQuery objects are basically wrapper objects around a set of DOM elements.
–
Retributive A note on the difference in speed. Attach the following snipet to an onclick call:
function myfunc()
{
var timer = new Date();
for(var i = 0; i < 10000; i++)
{
//document.getElementById('myID');
$('#myID')[0];
}
console.log('timer: ' + (new Date() - timer));
}
Alternate commenting one out and then comment the other out. In my tests,
document.getElementbyId averaged about 35ms (fluctuating from
25ms
up to52ms
on about15 runs
)
On the other hand, the
jQuery averaged about 200ms (ranging from
181ms
to222ms
on about15 runs
).From this simple test you can see that the jQuery took about 6 times as long.
Of course, that is over 10000
iterations so in a simpler situation I would probably use the jQuery for ease of use and all of the other cool things like .animate
and .fadeTo
. But yes, technically getElementById
is quite a bit faster.
$('#someID')
with document.getElementById("someID")
? I am working on something in which I have extensively used $('#someID')
and my page runs slow for big file inputs. Please suggest me what should be my move. –
Canterbury var $myId = $('#myId');
and reuse the saved variable $myId
. Finding by id is generally a pretty fast thing though so if the page is sluggish there is probably a different reason. –
Acantho Close, but not the same. They're getting the same element, but the jQuery version is wrapped in a jQuery object.
The equivalent would be this
var contents = $('#contents').get(0);
or this
var contents = $('#contents')[0];
These will pull the element out of the jQuery object.
No. The first returns a DOM element, or null, whereas the second always returns a jQuery object. The jQuery object will be empty if no element with the id of contents
was matched.
The DOM element returned by document.getElementById('contents')
allows you to do things such as change the .innerHTML
(or .value
) etc, however you'll need to use jQuery methods on the jQuery Object.
var contents = $('#contents').get(0);
Is more equivilent, however if no element with the id of contents
is matched, document.getElementById('contents')
will return null, but $('#contents').get(0)
will return undefined.
One benefit on using the jQuery object is that you won't get any errors if no elements were returned, as an object is always returned. However you will get errors if you try to perform operations on the null
returned by document.getElementById
No, actually the same result would be:
$('#contents')[0]
jQuery does not know how many results would be returned from the query. What you get back is a special jQuery object which is a collection of all the controls that matched the query.
Part of what makes jQuery so convenient is that MOST methods called on this object that look like they are meant for one control, are actually in a loop called on all the members int he collection
When you use the [0] syntax you take the first element from the inner collection. At this point you get a DOM object
In case someone else hits this... Here's another difference:
If the id contains characters that are not supported by the HTML standard (see SO question here) then jQuery may not find it even if getElementById does.
This happened to me with an id containing "/" characters (ex: id="a/b/c"), using Chrome:
var contents = document.getElementById('a/b/c');
was able to find my element but:
var contents = $('#a/b/c');
did not.
Btw, the simple fix was to move that id to the name field. JQuery had no trouble finding the element using:
var contents = $('.myclass[name='a/b/c']);
var contents = document.getElementById('contents');
var contents = $('#contents');
The code snippets are not the same. first one returns a Element
object (source).
The second one, jQuery equivalent will return a jQuery object containing a collection of either zero or one DOM element. (jQuery documentation). Internally jQuery uses document.getElementById()
for efficiency.
In both the cases if more than one element found only the first element will be returned.
When checking the github project for jQuery I found following line snippets which seems to be using document.getElementById codes (https://github.com/jquery/jquery/blob/master/src/core/init.js line 68 onwards)
// HANDLE: $(#id)
} else {
elem = document.getElementById( match[2] );
Just like most people have said, the main difference is the fact that it is wrapped in a jQuery object with the jQuery call vs the raw DOM object using straight JavaScript. The jQuery object will be able to do other jQuery functions with it of course but, if you just need to do simple DOM manipulation like basic styling or basic event handling, the straight JavaScript method is always a tad bit faster than jQuery since you don't have to load in an external library of code built on JavaScript. It saves an extra step.
One other difference: getElementById
returns the first match, while $('#...')
returns a collection of matches - yes, the same ID can be repeated in an HTML doc.
Further, getElementId
is called from the document, while $('#...')
can be called from a selector. So, in the code below, document.getElementById('content')
will return the entire body but $('form #content')[0]
will return inside of the form.
<body id="content">
<h1>Header!</h1>
<form>
<div id="content"> My Form </div>
</form>
</body>
It might seem odd to use duplicate IDs, but if you are using something like Wordpress, a template or plugin might use the same id as you use in the content. The selectivity of jQuery could help you out there.
jQuery is built over JavaScript. This means that it's just javascript anyway.
document.getElementById()
The document.getElementById() method returns the element that has the ID attribute with the specified value and Returns null if no elements with the specified ID exists.An ID should be unique within a page.
Jquery $()
Calling jQuery() or $() with an id selector as its argument will return a jQuery object containing a collection of either zero or one DOM element.Each id value must be used only once within a document. If more than one element has been assigned the same ID, queries that use that ID will only select the first matched element in the DOM.
All the answers are old today as of 2019 you can directly access id keyed filds in javascript simply try it
<p id="mytext"></p>
<script>mytext.innerText = 'Yes that works!'</script>
Online Demo! - https://codepen.io/frank-dspeed/pen/mdywbre
All the answers above are correct. In case you want to see it in action, don't forget you have Console in a browser where you can see the actual result crystal clear :
I have an HTML :
<div id="contents"></div>
Go to console (cntrl+shift+c)
and use these commands to see your result clearly
document.getElementById('contents')
>>> div#contents
$('#contents')
>>> [div#contents,
context: document,
selector: "#contents",
jquery: "1.10.1",
constructor: function,
init: function …]
As we can see, in the first case we got the tag itself (that is, strictly speaking, an HTMLDivElement object). In the latter we actually don’t have a plain object, but an array of objects. And as mentioned by other answers above, you can use the following command:
$('#contents')[0]
>>> div#contents
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