Related
So jQuery 1.6 has the new function prop().
$(selector).click(function(){
//instead of:
this.getAttribute('style');
//do i use:
$(this).prop('style');
//or:
$(this).attr('style');
})
or in this case do they do the same thing?
And if I do have to switch to using prop(), all the old attr() calls will break if i switch to 1.6?
UPDATE
selector = '#id'
$(selector).click(function() {
//instead of:
var getAtt = this.getAttribute('style');
//do i use:
var thisProp = $(this).prop('style');
//or:
var thisAttr = $(this).attr('style');
console.log(getAtt, thisProp, thisAttr);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.0/jquery.min.js"></script>
<div id='id' style="color: red;background: orange;">test</div>
(see also this fiddle: http://jsfiddle.net/maniator/JpUF2/)
The console logs the getAttribute as a string, and the attr as a string, but the prop as a CSSStyleDeclaration, Why? And how does that affect my coding in the future?
Update 1 November 2012
My original answer applies specifically to jQuery 1.6. My advice remains the same but jQuery 1.6.1 changed things slightly: in the face of the predicted pile of broken websites, the jQuery team reverted attr() to something close to (but not exactly the same as) its old behaviour for Boolean attributes. John Resig also blogged about it. I can see the difficulty they were in but still disagree with his recommendation to prefer attr().
Original answer
If you've only ever used jQuery and not the DOM directly, this could be a confusing change, although it is definitely an improvement conceptually. Not so good for the bazillions of sites using jQuery that will break as a result of this change though.
I'll summarize the main issues:
You usually want prop() rather than attr().
In the majority of cases, prop() does what attr() used to do. Replacing calls to attr() with prop() in your code will generally work.
Properties are generally simpler to deal with than attributes. An attribute value may only be a string whereas a property can be of any type. For example, the checked property is a Boolean, the style property is an object with individual properties for each style, the size property is a number.
Where both a property and an attribute with the same name exists, usually updating one will update the other, but this is not the case for certain attributes of inputs, such as value and checked: for these attributes, the property always represents the current state while the attribute (except in old versions of IE) corresponds to the default value/checkedness of the input (reflected in the defaultValue / defaultChecked property).
This change removes some of the layer of magic jQuery stuck in front of attributes and properties, meaning jQuery developers will have to learn a bit about the difference between properties and attributes. This is a good thing.
If you're a jQuery developer and are confused by this whole business about properties and attributes, you need to take a step back and learn a little about it, since jQuery is no longer trying so hard to shield you from this stuff. For the authoritative but somewhat dry word on the subject, there's the specs: DOM4, HTML DOM, DOM Level 2, DOM Level 3. Mozilla's DOM documentation is valid for most modern browsers and is easier to read than the specs, so you may find their DOM reference helpful. There's a section on element properties.
As an example of how properties are simpler to deal with than attributes, consider a checkbox that is initially checked. Here are two possible pieces of valid HTML to do this:
<input id="cb" type="checkbox" checked>
<input id="cb" type="checkbox" checked="checked">
So, how do you find out if the checkbox is checked with jQuery? Look on Stack Overflow and you'll commonly find the following suggestions:
if ( $("#cb").attr("checked") === true ) {...}
if ( $("#cb").attr("checked") == "checked" ) {...}
if ( $("#cb").is(":checked") ) {...}
This is actually the simplest thing in the world to do with the checked Boolean property, which has existed and worked flawlessly in every major scriptable browser since 1995:
if (document.getElementById("cb").checked) {...}
The property also makes checking or unchecking the checkbox trivial:
document.getElementById("cb").checked = false
In jQuery 1.6, this unambiguously becomes
$("#cb").prop("checked", false)
The idea of using the checked attribute for scripting a checkbox is unhelpful and unnecessary. The property is what you need.
It's not obvious what the correct way to check or uncheck the checkbox is using the checked attribute
The attribute value reflects the default rather than the current visible state (except in some older versions of IE, thus making things still harder). The attribute tells you nothing about the whether the checkbox on the page is checked. See http://jsfiddle.net/VktA6/49/.
I think Tim said it quite well, but let's step back:
A DOM element is an object, a thing in memory. Like most objects in OOP, it has properties. It also, separately, has a map of the attributes defined on the element (usually coming from the markup that the browser read to create the element). Some of the element's properties get their initial values from attributes with the same or similar names (value gets its initial value from the "value" attribute; href gets its initial value from the "href" attribute, but it's not exactly the same value; className from the "class" attribute). Other properties get their initial values in other ways: For instance, the parentNode property gets its value based on what its parent element is; an element always has a style property, whether it has a "style" attribute or not.
Let's consider this anchor in a page at http://example.com/testing.html:
<a href='foo.html' class='test one' name='fooAnchor' id='fooAnchor'>Hi</a>
Some gratuitous ASCII art (and leaving out a lot of stuff):
+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
| HTMLAnchorElement |
+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
| href: "http://example.com/foo.html" |
| name: "fooAnchor" |
| id: "fooAnchor" |
| className: "test one" |
| attributes: |
| href: "foo.html" |
| name: "fooAnchor" |
| id: "fooAnchor" |
| class: "test one" |
+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
Note that the properties and attributes are distinct.
Now, although they are distinct, because all of this evolved rather than being designed from the ground up, a number of properties write back to the attribute they derived from if you set them. But not all do, and as you can see from href above, the mapping is not always a straight "pass the value on", sometimes there's interpretation involved.
When I talk about properties being properties of an object, I'm not speaking in the abstract. Here's some non-jQuery code:
var link = document.getElementById('fooAnchor');
alert(link.href); // alerts "http://example.com/foo.html"
alert(link.getAttribute("href")); // alerts "foo.html"
(Those values are as per most browsers; there's some variation.)
The link object is a real thing, and you can see there's a real distinction between accessing a property on it, and accessing an attribute.
As Tim said, the vast majority of the time, we want to be working with properties. Partially that's because their values (even their names) tend to be more consistent across browsers. We mostly only want to work with attributes when there is no property related to it (custom attributes), or when we know that for that particular attribute, the attribute and the property are not 1:1 (as with href and "href" above).
The standard properties are laid out in the various DOM specs:
DOM2 HTML (largely obsolete, see the HTML spec instead)
DOM2 Core (obsolete)
DOM3 Core (obsolete)
DOM4
These specs have excellent indexes and I recommend keeping links to them handy; I use them all the time.
Custom attributes would include, for instance, any data-xyz attributes you might put on elements to provide meta-data to your code (now that that's valid as of HTML5, as long as you stick to the data- prefix). (Recent versions of jQuery give you access to data-xyz elements via the data function, but that function is not just an accessor for data-xyz attributes [it does both more and less than that]; unless you actually need its features, I'd use the attr function to interact with data-xyz attribute.)
The attr function used to have some convoluted logic around getting what they thought you wanted, rather than literally getting the attribute. It conflated the concepts. Moving to prop and attr was meant to de-conflate them. Briefly in v1.6.0 jQuery went too far in that regard, but functionality was quickly added back to attr to handle the common situations where people use attr when technically they should use prop.
This change has been a long time coming for jQuery. For years, they've been content with a function named attr() that mostly retrieved DOM properties, not the result you'd expect from the name. The segregation of attr() and prop() should help alleviate some of the confusion between HTML attributes and DOM properties. $.fn.prop() grabs the specified DOM property, while $.fn.attr() grabs the specified HTML attribute.
To fully understand how they work, here's an extended explanation on the difference between HTML attributes and DOM properties.:
HTML Attributes
Syntax:
<body onload="foo()">
Purpose:
Allows markup to have data associated with it for events, rendering, and other purposes.
Visualization:
The class attribute is shown here on the body. It's accessible through the following code:
var attr;
attr = document.body.getAttribute("class");
//IE 8 Quirks and below
attr = document.body.getAttribute("className");
Attributes are returned in string form and can be inconsistent from browser to browser. However, they can be vital in some situations. As exemplified above, IE 8 Quirks Mode (and below) expects the name of a DOM property in get/set/removeAttribute instead of the attribute name. This is one of many reasons why it's important to know the difference.
DOM Properties
Syntax:
document.body.onload = foo;
Purpose:
Gives access to properties that belong to element nodes. These properties are similar to attributes, but are only accessible through JavaScript. This is an important difference that helps clarify the role of DOM properties. Please note that attributes are completely different from properties, as this event handler assignment is useless and won't receive the event (body doesn't have an onload event, only an onload attribute).
Visualization:
Here, you'll notice a list of properties under the "DOM" tab in Firebug. These are DOM properties. You'll immediately notice quite a few of them, as you'll have used them before without knowing it. Their values are what you'll be receiving through JavaScript.
Documentation
JavaScript: The Definitive Guide by
David Flanagan
HTML Attributes,
Mozilla Dev Center
DOM Element Properties, Mozilla Dev Center
Example
HTML: <textarea id="test" value="foo"></textarea>
JavaScript: alert($('#test').attr('value'));
In earlier versions of jQuery, this returns an empty string. In 1.6, it returns the proper value, foo.
Without having glanced at the new code for either function, I can say with confidence that the confusion has more to do with the difference between HTML attributes and DOM properties, than with the code itself. Hopefully, this cleared some things up for you.
-Matt
A property is in the DOM; an attribute is in the HTML that is parsed into the DOM.
Further detail
If you change an attribute, the change will be reflected in the DOM (sometimes with a different name).
Example: Changing the class attribute of a tag will change the className property of that tag in the DOM (That's because class is already used).
If you have no attribute on a tag, you still have the corresponding DOM property with an empty or a default value.
Example: While your tag has no class attribute, the DOM property className does exist with a empty string value.
edit
If you change the one, the other will be changed by a controller, and vice versa.
This controller is not in jQuery, but in the browser's native code.
It's just the distinction between HTML attributes and DOM objects that causes a confusion. For those that are comfortable acting on the DOM elements native properties such a this.src this.value this.checked etc, .prop is a very warm welcome to the family. For others, it's just an added layer of confusion. Let's clear that up.
The easiest way to see the difference between .attr and .prop is the following example:
<input blah="hello">
$('input').attr('blah'): returns 'hello' as expected. No suprises here.
$('input').prop('blah'): returns undefined -- because it's trying to do [HTMLInputElement].blah -- and no such property on that DOM object exists. It only exists in the scope as an attribute of that element i.e. [HTMLInputElement].getAttribute('blah')
Now we change a few things like so:
$('input').attr('blah', 'apple');
$('input').prop('blah', 'pear');
$('input').attr('blah'): returns 'apple' eh? Why not "pear" as this was set last on that element. Because the property was changed on the input attribute, not the DOM input element itself -- they basically almost work independently of each other.
$('input').prop('blah'): returns 'pear'
The thing you really need to be careful with is just do not mix the usage of these for the same property throughout your application for the above reason.
See a fiddle demonstrating the difference: http://jsfiddle.net/garreh/uLQXc/
.attr vs .prop:
Round 1: style
<input style="font:arial;"/>
.attr('style') -- returns inline styles for the matched element i.e. "font:arial;"
.prop('style') -- returns an style declaration object i.e. CSSStyleDeclaration
Round 2: value
<input value="hello" type="text"/>
$('input').prop('value', 'i changed the value');
.attr('value') -- returns 'hello' *
.prop('value') -- returns 'i changed the value'
* Note: jQuery for this reason has a .val() method, which internally is equivalent to .prop('value')
TL;DR
Use prop() over attr() in the majority of cases.
A property is the current state of the input element. An attribute is the default value.
A property can contain things of different types. An attribute can only contain strings
Dirty checkedness
This concept provides an example where the difference is observable: http://www.w3.org/TR/html5/forms.html#concept-input-checked-dirty
Try it out:
click the button. Both checkboxes got checked.
uncheck both checkboxes.
click the button again. Only the prop checkbox got checked. BANG!
$('button').on('click', function() {
$('#attr').attr('checked', 'checked')
$('#prop').prop('checked', true)
})
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<label>attr <input id="attr" type="checkbox"></label>
<label>prop <input id="prop" type="checkbox"></label>
<button type="button">Set checked attr and prop.</button>
For some attributes like disabled on button, adding or removing the content attribute disabled="disabled" always toggles the property (called IDL attribute in HTML5) because http://www.w3.org/TR/html5/forms.html#attr-fe-disabled says:
The disabled IDL attribute must reflect the disabled content attribute.
so you might get away with it, although it is ugly since it modifies HTML without need.
For other attributes like checked="checked" on input type="checkbox", things break, because once you click on it, it becomes dirty, and then adding or removing the checked="checked" content attribute does not toggle checkedness anymore.
This is why you should use mostly .prop, as it affects the effective property directly, instead of relying on complex side-effects of modifying the HTML.
All is in the doc:
The difference between attributes and properties can be important in specific situations. Before jQuery 1.6, the .attr() method sometimes took property values into account when retrieving some attributes, which could cause inconsistent behavior. As of jQuery 1.6, the .prop() method provides a way to explicitly retrieve property values, while .attr() retrieves attributes.
So use prop!
attributes are in your HTML text document/file (== imagine this is the result of your html markup parsed), whereas
properties are in HTML DOM tree (== basically an actual property of some object in JS sense).
Importantly, many of them are synced (if you update class property, class attribute in html will also be updated; and otherwise). But some attributes may be synced to unexpected properties - eg, attribute checked corresponds to property defaultChecked, so that
manually checking a checkbox will change .prop('checked') value, but will not change .attr('checked') and .prop('defaultChecked') values
setting $('#input').prop('defaultChecked', true) will also change .attr('checked'), but this will not be visible on an element.
Rule of thumb is: .prop() method should be used for boolean attributes/properties and for properties which do not exist in html
(such as window.location). All other attributes (ones you can see in
the html) can and should continue to be manipulated with the .attr()
method. (http://blog.jquery.com/2011/05/10/jquery-1-6-1-rc-1-released/)
And here is a table that shows where .prop() is preferred (even though .attr() can still be used).
Why would you sometimes want to use .prop() instead of .attr() where latter is officially adviced?
.prop() can return any type - string, integer, boolean; while .attr() always returns a string.
.prop() is said to be about 2.5 times faster than .attr().
.attr():
Get the value of an attribute for the first element in the set of matched elements.
Gives you the value of element as it was defined in the html on page load
.prop():
Get the value of a property for the first element in the set of matched elements.
Gives the updated values of elements which is modified via javascript/jquery
Usually you'll want to use properties.
Use attributes only for:
Getting a custom HTML attribute (since it's not synced with a DOM property).
Getting a HTML attribute that doesn't sync with a DOM property, e.g. get the "original value" of a standard HTML attribute, like <input value="abc">.
attributes -> HTML
properties -> DOM
Before jQuery 1.6 , the attr() method sometimes took property values into account when retrieving attributes, this caused rather inconsistent behavior.
The introduction of the prop() method provides a way to explicitly retrieve property values, while .attr() retrieves attributes.
The Docs:
jQuery.attr()
Get the value of an attribute for the first element in the set of matched elements.
jQuery.prop()
Get the value of a property for the first element in the set of matched elements.
One thing .attr() can do that .prop() can't: affect CSS selectors
Here's an issue I didn't see in the other answers.
CSS selector [name=value]
will respond to .attr('name', 'value')
but not always to .prop('name', 'value')
.prop() affects only a few attribute-selectors
input[name] (thanks #TimDown)
.attr() affects all attribute-selectors
input[value]
input[naame]
span[name]
input[data-custom-attribute] (neither will .data('custom-attribute') affect this selector)
Gently reminder about using prop(), example:
if ($("#checkbox1").prop('checked')) {
isDelete = 1;
} else {
isDelete = 0;
}
The function above is used to check if checkbox1 is checked or not, if checked: return 1; if not: return 0. Function prop() used here as a GET function.
if ($("#checkbox1").prop('checked', true)) {
isDelete = 1;
} else {
isDelete = 0;
}
The function above is used to set checkbox1 to be checked and ALWAYS return 1. Now function prop() used as a SET function.
Don't mess up.
P/S: When I'm checking Image src property. If the src is empty, prop return the current URL of the page (wrong), and attr return empty string (right).
1) A property is in the DOM; an attribute is in the HTML that is
parsed into the DOM.
2) $( elem ).attr( "checked" ) (1.6.1+) "checked" (String) Will
change with checkbox state
3) $( elem ).attr( "checked" ) (pre-1.6) true (Boolean) Changed
with checkbox state
Mostly we want to use for DOM object rather then custom attribute
like data-img, data-xyz.
Also some of difference when accessing checkbox value and href
with attr() and prop() as thing change with DOM output with
prop() as full link from origin and Boolean value for checkbox
(pre-1.6)
We can only access DOM elements with prop other then it gives undefined
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.0/jquery.min.js"></script>
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>prop demo</title>
<style>
p {
margin: 20px 0 0;
}
b {
color: blue;
}
</style>
</head>
<body>
<input id="check1" type="checkbox" checked="checked">
<label for="check1">Check me</label>
<p></p>
<script>
$("input").change(function() {
var $input = $(this);
$("p").html(
".attr( \"checked\" ): <b>" + $input.attr("checked") + "</b><br>" +
".prop( \"checked\" ): <b>" + $input.prop("checked") + "</b><br>" +
".is( \":checked\" ): <b>" + $input.is(":checked")) + "</b>";
}).change();
</script>
</body>
</html>
There are few more considerations in prop() vs attr():
selectedIndex, tagName, nodeName, nodeType, ownerDocument, defaultChecked, and defaultSelected..etc should be retrieved and set with the .prop() method. These do not have corresponding attributes and are only properties.
For input type checkbox
.attr('checked') //returns checked
.prop('checked') //returns true
.is(':checked') //returns true
prop method returns Boolean value for checked, selected, disabled,
readOnly..etc while attr returns defined string. So, you can directly
use .prop(‘checked’) in if condition.
.attr() calls .prop() internally so .attr() method will be slightly
slower than accessing them directly through .prop().
Gary Hole answer is very relevant to solve the problem if the code is written in such way
obj.prop("style","border:1px red solid;")
Since the prop function return CSSStyleDeclaration object, above code will not working properly in some browser(tested with IE8 with Chrome Frame Plugin in my case).
Thus changing it into following code
obj.prop("style").cssText = "border:1px red solid;"
solved the problem.
Please take time to read the question in full before assuming that it's a duplicate of .prop() vs .attr()
I've read .prop() vs .attr() and a handful of the duplicates and related non-duplicates. My question is: when is it appropriate to pass values to .attr() when dealing with HTML and the DOM?
Of course the simple answer is "why, whenever you wish to set or modify the value of an attribute - otherwise (and usually) use .prop()."
But what I really want to know is when should you wish to. In the jQuery docs for the method, I see examples of setting things like id, src alt, and title on img elements. But the docs don't seem to give any indication of why you may want to do so, over using .prop() to set these particular attributes.
What I'm after is a guiding principle of when to use .attr() to set things rather than .prop().
Related note: the particular case I'm working on is what's the proper way to change the action on a form, but really I want the perspective and understanding behind the decision.
edit To clarify, I am not looking for:
the differences between properties and attributes
the differences between .attr() and .prop()
the differences between using .attr() and .prop() to get values for either attributes or properties
Otherwise, we could just mark this as a duplicate and call it a day :) No offense intended whatsoever to what's been offered so far - just wanted to make it clear that I'm looking for info on what determines when it's right to use .attr() to set the attribute value, which info I did not find on the venerable .prop() vs .attr() (though if it's there and I missed it, let's definitely mark this as a duplicate!) Thanks!
From http://jq4you.blogspot.in/2013/04/jquery-attr-vs-prop-difference.html:
Jquery attr() vs prop()
jQuery.attr()
Get the value of an attribute for the first element in the set of matched elements.
whereas,
jQuery.prop()
Get the value of a property for the first element in the set of matched elements.
Before jQuery 1.6 , the attr() method sometimes took property values into account when retrieving some attributes, which caused in
inconsistent behavior. And thus, the prop() method was introduced. As
of jQuery 1.6. , the .prop() method provides a way to explicitly
retrieve property values, while .attr() retrieves attributes.
What actually is Attributes?
Attributes carry additional information about an HTML element and come
in name=”value” pairs. You can set an attribute for HTML element and
define it while writing the source code.
simple example can be:
<input id="test" type="test" value="test">
here, "type","value", "id" are attributes of the input elements.
From .prop() vs .attr():
I'll summarize the main issues:
You usually want prop() rather than attr().
In the majority of cases, prop() does what attr() used to do. Replacing calls to attr() with prop() in your code will generally
work.
Properties are generally simpler to deal with than attributes.
An attribute value may only be a string whereas a property can be of any type. For example, the checked property is a Boolean, the
style property is an object with individual properties for each
style, the size property is a number.
Where both a property and an attribute with the same name exists, usually updating one will update the other, but this is not the case
for certain attributes of inputs, such as value and checked: for
these attributes, the property always represents the current state
while the attribute (except in old versions of IE) corresponds to the
default value/checkedness of the input (reflected in the defaultValue
/ defaultChecked property).
This change removes some of the layer of magic jQuery stuck in front of attributes and properties, meaning jQuery developers will
have to learn a bit about the difference between properties and
attributes. This is a good thing.
Jsfiddle try yourself
After lots of reading and re-reading, I think the answer is this. (And rather than try to extract just the part of this that applies to the original question, I think it makes sense to give the full set of 'rules' for context.)
1. Use .attr() only when
getting/setting data-* attributes
working with an attribute/property pair that aren't 1:1 (like href on an anchor element)
2. Use .prop() in all other cases
3. Except for value. Use .val() to get/set an input's value.
Don't use .attr('value')
Don't use .attr('value', 'foo')
Don't use .prop('value')
Don't use .prop('value', 'foo')
I think by following these rules the answer to the question of what happens to properties when you pass a value to .attr() ends up being "who cares?". And the answer of what .attr('foo', 'bar') would be useful for if the now-deprecated use of .attr() to set property values were to be removed ends up being "to set/modify data-* attributes".
If anyone else can think of other cases when using .attr() would be preferable to using .prop() please chime in.
I have a modal form that is generated using bootstrap 3. It doesn't look like there is a reliable way to determine when that form is being shown onscreen. I am attempting to create one. I attached two events to my DOM element that signal when it is shown and when it is hidden.
jq_modal_login_form = $('#modal-login-form')[0]
jq_modal_login_form.on('shown.bs.modal', function () {
jq_modal_login_form.active_onscreen = true;
});
jq_modal_login_form.on('hidden.bs.modal', function () {
jq_modal_login_form.active_onscreen = false;
});
I tried to give an attribute named active_onscreen to the DOM element above. When I look at the DOM element in the debugger later, the attribute is not present.
I should mention that I am VERY new to javascript. Is attribute even the right word to use here? It looks like attribute is a bit of a misnomer as well. It could be an attribute of the object but could also be an attribute of the object.attributes attribute, right? I assume the later is where styling ect., goes and is not what I want to change. Does anyone have some insight as to what I should be doing here?
In jQuery:
$('selector').attr('attribute_name', 'value');
However, you can should only use predefined attributes as creating custom attributes requires additional setup (see this question) that is not necessary in your case.
In your case, you may just want to add a active_onscreen class to the element. Classes are meant to be used to identify elements (and not just for CSS), so they are perfect for this applicaiton. You would use this to add a class to an element:
$('selector').addClass('active_onscreen').
When it is no longer active, you would use this to remove the class:
$('selector').removeClass('active_onscreen').
What you are doing here is adding a property of the DOM object - not an attribute of the element.
Adding an attribute does not necessarily make the property mirror it. Only built-in properties do this.
If you want to set an attribute, but not the property, you can use jQuery's .attr() method.
If you just want to see if a given modal is open, Bootstrap does that for you. You can check the bs.modal data attribute:
$("element").data('bs.modal').isShown;
or a class (but this method is prone to race conditions):
$('#myModal').hasClass('in');
After reading (the interesting) .prop() vs .attr() and jQuery Performance : attributes doubt arise in my mind about what is better to use: .prop() or .val() ? I want to set an input text value.
The jQuery .prop() page said the following:
Properties generally affect the dynamic state of a DOM element without changing the serialized HTML attribute. Examples include the value property of input elements, the disabled property of inputs and buttons, or the checked property of a checkbox. The .prop() method should be used to set disabled and checked instead of the .attr() method. The .val() method should be used for getting and setting value.
But regarding to performance .prop() seems to be better than .val() setting values:
So I don't have an answer.
What I should do?
$('#element').prop('value', 'Example');
or
$('#element').val('Example');
EDIT1:
.prop() is always better than .val()
EDIT2:
I've tried now getting a value, also .prop() is faster
EDIT3:
As #BeatAlex says if we want performace native js is extremely faster
var x = document.getElementById('element').value;
As some of you said it may be faster, but if .val() exist we'd use it.
PS: while I am writing this, current jQuery version is 1.11 or 2.1
You want to use val(). That's what the function is for, specifically for the value of the input.
It's also quicker to write, easier to understand and while using val, you can change the value multiple times if need be.
Your chart says
Higher is better
and val() higher.
Also, like you've already quoted,
The .val() method should be used for getting and setting value.
This means that unless you're dealing with disabled properties, use:
$('input').val();
Also as a side note, the link you posted, after running tests, shows that val() is faster than prop().
Since you LOVE to show some graphs and pictures, i'm going to add some:
Taken from this link
Pure JS is better if you're arguing over speed.
Dude, you cannot compare prop to val, that makes no sense!
val is designed to set/get the attribute "value" from the current selected node(s). So that's the only method you need for your use-case. (I want to set an input text value).
Of course you can workaround val by using attr('value') or prop('value') but why do you want to make boilerplate code?
You seem to be confused on what prop was designed for. So let me explain a little.
prop was designed to solve the issue of retrieving Boolean-like properties from the selected DOM node. It should be compared to the method attr not to val
Consider the following four cases
<input type="checkbox" checked />
<input type="checkbox" checked="checked" />
<input type="checkbox" checked="false" />
<input type="checkbox" checked="true" />
You will never ever get the state checked/unchecked of the input using val()
You are not sure what is the checked state of the control if you retrieve it using attr('checked'). This will give you back a string.
If you use the result of attr('checked') inside of an if statement, you are at risk of getting false positives, e.g., if('false')
The only way to consistently get the checked state out of the control is by using the prop method.
So if you wanna make a real comparison please compare it to attr, not to val
The other answers explain the main differences pretty well with one exception.
Since jQuery "normalizes" browser differences val() removes carriage returns.
This affects textareas in IE 8 and below.
Example:
For the textarea input of
HEL
LO
.val() gives you the string "HEL\n\nLO" and a length of 7
.prop("value") gives you the string "HEL\r\n\r\nLO" with a length of 9
Your charts are indicating that prop() is better than val() in terms of performance.
val() could be internally using the same logic of prop() along with some additional code statements for completing the actual operation(Ex: setting value), that additional code of val() might lead to little low performance than prop().
It would be nice to use val() for setting a value for an element perhaps that is what this function is meant for, in general it's preferred to go with the operation specific functions instead of using the generic ones.
In your case, if you don't want to loose even a slight variation in performance then go with prop() itself.
That's not a question of performance, they are actually made for quite different things. jQuery seems to have decided to handled "out of spec" usecase, probably for good reason.
attr() is to access the HTML attribute of the element. More probably the initial value as when the page loaded. It though has been altered by the write version of attr() or any other attribute manipulation function
prop() is to access the DOM property of the element, after it has been parsed and displayed.
val() is to access a form element value.
One more bug when using prop(). Under IE 11, the following code wouldn't set the value:
var props = {'value':'test', 'type':'radio'};
var input = $('<input/>').prop(props);
$(document.body).append(input);
So jQuery 1.6 has the new function prop().
$(selector).click(function(){
//instead of:
this.getAttribute('style');
//do i use:
$(this).prop('style');
//or:
$(this).attr('style');
})
or in this case do they do the same thing?
And if I do have to switch to using prop(), all the old attr() calls will break if i switch to 1.6?
UPDATE
selector = '#id'
$(selector).click(function() {
//instead of:
var getAtt = this.getAttribute('style');
//do i use:
var thisProp = $(this).prop('style');
//or:
var thisAttr = $(this).attr('style');
console.log(getAtt, thisProp, thisAttr);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.0/jquery.min.js"></script>
<div id='id' style="color: red;background: orange;">test</div>
(see also this fiddle: http://jsfiddle.net/maniator/JpUF2/)
The console logs the getAttribute as a string, and the attr as a string, but the prop as a CSSStyleDeclaration, Why? And how does that affect my coding in the future?
Update 1 November 2012
My original answer applies specifically to jQuery 1.6. My advice remains the same but jQuery 1.6.1 changed things slightly: in the face of the predicted pile of broken websites, the jQuery team reverted attr() to something close to (but not exactly the same as) its old behaviour for Boolean attributes. John Resig also blogged about it. I can see the difficulty they were in but still disagree with his recommendation to prefer attr().
Original answer
If you've only ever used jQuery and not the DOM directly, this could be a confusing change, although it is definitely an improvement conceptually. Not so good for the bazillions of sites using jQuery that will break as a result of this change though.
I'll summarize the main issues:
You usually want prop() rather than attr().
In the majority of cases, prop() does what attr() used to do. Replacing calls to attr() with prop() in your code will generally work.
Properties are generally simpler to deal with than attributes. An attribute value may only be a string whereas a property can be of any type. For example, the checked property is a Boolean, the style property is an object with individual properties for each style, the size property is a number.
Where both a property and an attribute with the same name exists, usually updating one will update the other, but this is not the case for certain attributes of inputs, such as value and checked: for these attributes, the property always represents the current state while the attribute (except in old versions of IE) corresponds to the default value/checkedness of the input (reflected in the defaultValue / defaultChecked property).
This change removes some of the layer of magic jQuery stuck in front of attributes and properties, meaning jQuery developers will have to learn a bit about the difference between properties and attributes. This is a good thing.
If you're a jQuery developer and are confused by this whole business about properties and attributes, you need to take a step back and learn a little about it, since jQuery is no longer trying so hard to shield you from this stuff. For the authoritative but somewhat dry word on the subject, there's the specs: DOM4, HTML DOM, DOM Level 2, DOM Level 3. Mozilla's DOM documentation is valid for most modern browsers and is easier to read than the specs, so you may find their DOM reference helpful. There's a section on element properties.
As an example of how properties are simpler to deal with than attributes, consider a checkbox that is initially checked. Here are two possible pieces of valid HTML to do this:
<input id="cb" type="checkbox" checked>
<input id="cb" type="checkbox" checked="checked">
So, how do you find out if the checkbox is checked with jQuery? Look on Stack Overflow and you'll commonly find the following suggestions:
if ( $("#cb").attr("checked") === true ) {...}
if ( $("#cb").attr("checked") == "checked" ) {...}
if ( $("#cb").is(":checked") ) {...}
This is actually the simplest thing in the world to do with the checked Boolean property, which has existed and worked flawlessly in every major scriptable browser since 1995:
if (document.getElementById("cb").checked) {...}
The property also makes checking or unchecking the checkbox trivial:
document.getElementById("cb").checked = false
In jQuery 1.6, this unambiguously becomes
$("#cb").prop("checked", false)
The idea of using the checked attribute for scripting a checkbox is unhelpful and unnecessary. The property is what you need.
It's not obvious what the correct way to check or uncheck the checkbox is using the checked attribute
The attribute value reflects the default rather than the current visible state (except in some older versions of IE, thus making things still harder). The attribute tells you nothing about the whether the checkbox on the page is checked. See http://jsfiddle.net/VktA6/49/.
I think Tim said it quite well, but let's step back:
A DOM element is an object, a thing in memory. Like most objects in OOP, it has properties. It also, separately, has a map of the attributes defined on the element (usually coming from the markup that the browser read to create the element). Some of the element's properties get their initial values from attributes with the same or similar names (value gets its initial value from the "value" attribute; href gets its initial value from the "href" attribute, but it's not exactly the same value; className from the "class" attribute). Other properties get their initial values in other ways: For instance, the parentNode property gets its value based on what its parent element is; an element always has a style property, whether it has a "style" attribute or not.
Let's consider this anchor in a page at http://example.com/testing.html:
<a href='foo.html' class='test one' name='fooAnchor' id='fooAnchor'>Hi</a>
Some gratuitous ASCII art (and leaving out a lot of stuff):
+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
| HTMLAnchorElement |
+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
| href: "http://example.com/foo.html" |
| name: "fooAnchor" |
| id: "fooAnchor" |
| className: "test one" |
| attributes: |
| href: "foo.html" |
| name: "fooAnchor" |
| id: "fooAnchor" |
| class: "test one" |
+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
Note that the properties and attributes are distinct.
Now, although they are distinct, because all of this evolved rather than being designed from the ground up, a number of properties write back to the attribute they derived from if you set them. But not all do, and as you can see from href above, the mapping is not always a straight "pass the value on", sometimes there's interpretation involved.
When I talk about properties being properties of an object, I'm not speaking in the abstract. Here's some non-jQuery code:
var link = document.getElementById('fooAnchor');
alert(link.href); // alerts "http://example.com/foo.html"
alert(link.getAttribute("href")); // alerts "foo.html"
(Those values are as per most browsers; there's some variation.)
The link object is a real thing, and you can see there's a real distinction between accessing a property on it, and accessing an attribute.
As Tim said, the vast majority of the time, we want to be working with properties. Partially that's because their values (even their names) tend to be more consistent across browsers. We mostly only want to work with attributes when there is no property related to it (custom attributes), or when we know that for that particular attribute, the attribute and the property are not 1:1 (as with href and "href" above).
The standard properties are laid out in the various DOM specs:
DOM2 HTML (largely obsolete, see the HTML spec instead)
DOM2 Core (obsolete)
DOM3 Core (obsolete)
DOM4
These specs have excellent indexes and I recommend keeping links to them handy; I use them all the time.
Custom attributes would include, for instance, any data-xyz attributes you might put on elements to provide meta-data to your code (now that that's valid as of HTML5, as long as you stick to the data- prefix). (Recent versions of jQuery give you access to data-xyz elements via the data function, but that function is not just an accessor for data-xyz attributes [it does both more and less than that]; unless you actually need its features, I'd use the attr function to interact with data-xyz attribute.)
The attr function used to have some convoluted logic around getting what they thought you wanted, rather than literally getting the attribute. It conflated the concepts. Moving to prop and attr was meant to de-conflate them. Briefly in v1.6.0 jQuery went too far in that regard, but functionality was quickly added back to attr to handle the common situations where people use attr when technically they should use prop.
This change has been a long time coming for jQuery. For years, they've been content with a function named attr() that mostly retrieved DOM properties, not the result you'd expect from the name. The segregation of attr() and prop() should help alleviate some of the confusion between HTML attributes and DOM properties. $.fn.prop() grabs the specified DOM property, while $.fn.attr() grabs the specified HTML attribute.
To fully understand how they work, here's an extended explanation on the difference between HTML attributes and DOM properties.:
HTML Attributes
Syntax:
<body onload="foo()">
Purpose:
Allows markup to have data associated with it for events, rendering, and other purposes.
Visualization:
The class attribute is shown here on the body. It's accessible through the following code:
var attr;
attr = document.body.getAttribute("class");
//IE 8 Quirks and below
attr = document.body.getAttribute("className");
Attributes are returned in string form and can be inconsistent from browser to browser. However, they can be vital in some situations. As exemplified above, IE 8 Quirks Mode (and below) expects the name of a DOM property in get/set/removeAttribute instead of the attribute name. This is one of many reasons why it's important to know the difference.
DOM Properties
Syntax:
document.body.onload = foo;
Purpose:
Gives access to properties that belong to element nodes. These properties are similar to attributes, but are only accessible through JavaScript. This is an important difference that helps clarify the role of DOM properties. Please note that attributes are completely different from properties, as this event handler assignment is useless and won't receive the event (body doesn't have an onload event, only an onload attribute).
Visualization:
Here, you'll notice a list of properties under the "DOM" tab in Firebug. These are DOM properties. You'll immediately notice quite a few of them, as you'll have used them before without knowing it. Their values are what you'll be receiving through JavaScript.
Documentation
JavaScript: The Definitive Guide by
David Flanagan
HTML Attributes,
Mozilla Dev Center
DOM Element Properties, Mozilla Dev Center
Example
HTML: <textarea id="test" value="foo"></textarea>
JavaScript: alert($('#test').attr('value'));
In earlier versions of jQuery, this returns an empty string. In 1.6, it returns the proper value, foo.
Without having glanced at the new code for either function, I can say with confidence that the confusion has more to do with the difference between HTML attributes and DOM properties, than with the code itself. Hopefully, this cleared some things up for you.
-Matt
A property is in the DOM; an attribute is in the HTML that is parsed into the DOM.
Further detail
If you change an attribute, the change will be reflected in the DOM (sometimes with a different name).
Example: Changing the class attribute of a tag will change the className property of that tag in the DOM (That's because class is already used).
If you have no attribute on a tag, you still have the corresponding DOM property with an empty or a default value.
Example: While your tag has no class attribute, the DOM property className does exist with a empty string value.
edit
If you change the one, the other will be changed by a controller, and vice versa.
This controller is not in jQuery, but in the browser's native code.
It's just the distinction between HTML attributes and DOM objects that causes a confusion. For those that are comfortable acting on the DOM elements native properties such a this.src this.value this.checked etc, .prop is a very warm welcome to the family. For others, it's just an added layer of confusion. Let's clear that up.
The easiest way to see the difference between .attr and .prop is the following example:
<input blah="hello">
$('input').attr('blah'): returns 'hello' as expected. No suprises here.
$('input').prop('blah'): returns undefined -- because it's trying to do [HTMLInputElement].blah -- and no such property on that DOM object exists. It only exists in the scope as an attribute of that element i.e. [HTMLInputElement].getAttribute('blah')
Now we change a few things like so:
$('input').attr('blah', 'apple');
$('input').prop('blah', 'pear');
$('input').attr('blah'): returns 'apple' eh? Why not "pear" as this was set last on that element. Because the property was changed on the input attribute, not the DOM input element itself -- they basically almost work independently of each other.
$('input').prop('blah'): returns 'pear'
The thing you really need to be careful with is just do not mix the usage of these for the same property throughout your application for the above reason.
See a fiddle demonstrating the difference: http://jsfiddle.net/garreh/uLQXc/
.attr vs .prop:
Round 1: style
<input style="font:arial;"/>
.attr('style') -- returns inline styles for the matched element i.e. "font:arial;"
.prop('style') -- returns an style declaration object i.e. CSSStyleDeclaration
Round 2: value
<input value="hello" type="text"/>
$('input').prop('value', 'i changed the value');
.attr('value') -- returns 'hello' *
.prop('value') -- returns 'i changed the value'
* Note: jQuery for this reason has a .val() method, which internally is equivalent to .prop('value')
TL;DR
Use prop() over attr() in the majority of cases.
A property is the current state of the input element. An attribute is the default value.
A property can contain things of different types. An attribute can only contain strings
Dirty checkedness
This concept provides an example where the difference is observable: http://www.w3.org/TR/html5/forms.html#concept-input-checked-dirty
Try it out:
click the button. Both checkboxes got checked.
uncheck both checkboxes.
click the button again. Only the prop checkbox got checked. BANG!
$('button').on('click', function() {
$('#attr').attr('checked', 'checked')
$('#prop').prop('checked', true)
})
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<label>attr <input id="attr" type="checkbox"></label>
<label>prop <input id="prop" type="checkbox"></label>
<button type="button">Set checked attr and prop.</button>
For some attributes like disabled on button, adding or removing the content attribute disabled="disabled" always toggles the property (called IDL attribute in HTML5) because http://www.w3.org/TR/html5/forms.html#attr-fe-disabled says:
The disabled IDL attribute must reflect the disabled content attribute.
so you might get away with it, although it is ugly since it modifies HTML without need.
For other attributes like checked="checked" on input type="checkbox", things break, because once you click on it, it becomes dirty, and then adding or removing the checked="checked" content attribute does not toggle checkedness anymore.
This is why you should use mostly .prop, as it affects the effective property directly, instead of relying on complex side-effects of modifying the HTML.
All is in the doc:
The difference between attributes and properties can be important in specific situations. Before jQuery 1.6, the .attr() method sometimes took property values into account when retrieving some attributes, which could cause inconsistent behavior. As of jQuery 1.6, the .prop() method provides a way to explicitly retrieve property values, while .attr() retrieves attributes.
So use prop!
attributes are in your HTML text document/file (== imagine this is the result of your html markup parsed), whereas
properties are in HTML DOM tree (== basically an actual property of some object in JS sense).
Importantly, many of them are synced (if you update class property, class attribute in html will also be updated; and otherwise). But some attributes may be synced to unexpected properties - eg, attribute checked corresponds to property defaultChecked, so that
manually checking a checkbox will change .prop('checked') value, but will not change .attr('checked') and .prop('defaultChecked') values
setting $('#input').prop('defaultChecked', true) will also change .attr('checked'), but this will not be visible on an element.
Rule of thumb is: .prop() method should be used for boolean attributes/properties and for properties which do not exist in html
(such as window.location). All other attributes (ones you can see in
the html) can and should continue to be manipulated with the .attr()
method. (http://blog.jquery.com/2011/05/10/jquery-1-6-1-rc-1-released/)
And here is a table that shows where .prop() is preferred (even though .attr() can still be used).
Why would you sometimes want to use .prop() instead of .attr() where latter is officially adviced?
.prop() can return any type - string, integer, boolean; while .attr() always returns a string.
.prop() is said to be about 2.5 times faster than .attr().
.attr():
Get the value of an attribute for the first element in the set of matched elements.
Gives you the value of element as it was defined in the html on page load
.prop():
Get the value of a property for the first element in the set of matched elements.
Gives the updated values of elements which is modified via javascript/jquery
Usually you'll want to use properties.
Use attributes only for:
Getting a custom HTML attribute (since it's not synced with a DOM property).
Getting a HTML attribute that doesn't sync with a DOM property, e.g. get the "original value" of a standard HTML attribute, like <input value="abc">.
attributes -> HTML
properties -> DOM
Before jQuery 1.6 , the attr() method sometimes took property values into account when retrieving attributes, this caused rather inconsistent behavior.
The introduction of the prop() method provides a way to explicitly retrieve property values, while .attr() retrieves attributes.
The Docs:
jQuery.attr()
Get the value of an attribute for the first element in the set of matched elements.
jQuery.prop()
Get the value of a property for the first element in the set of matched elements.
One thing .attr() can do that .prop() can't: affect CSS selectors
Here's an issue I didn't see in the other answers.
CSS selector [name=value]
will respond to .attr('name', 'value')
but not always to .prop('name', 'value')
.prop() affects only a few attribute-selectors
input[name] (thanks #TimDown)
.attr() affects all attribute-selectors
input[value]
input[naame]
span[name]
input[data-custom-attribute] (neither will .data('custom-attribute') affect this selector)
Gently reminder about using prop(), example:
if ($("#checkbox1").prop('checked')) {
isDelete = 1;
} else {
isDelete = 0;
}
The function above is used to check if checkbox1 is checked or not, if checked: return 1; if not: return 0. Function prop() used here as a GET function.
if ($("#checkbox1").prop('checked', true)) {
isDelete = 1;
} else {
isDelete = 0;
}
The function above is used to set checkbox1 to be checked and ALWAYS return 1. Now function prop() used as a SET function.
Don't mess up.
P/S: When I'm checking Image src property. If the src is empty, prop return the current URL of the page (wrong), and attr return empty string (right).
1) A property is in the DOM; an attribute is in the HTML that is
parsed into the DOM.
2) $( elem ).attr( "checked" ) (1.6.1+) "checked" (String) Will
change with checkbox state
3) $( elem ).attr( "checked" ) (pre-1.6) true (Boolean) Changed
with checkbox state
Mostly we want to use for DOM object rather then custom attribute
like data-img, data-xyz.
Also some of difference when accessing checkbox value and href
with attr() and prop() as thing change with DOM output with
prop() as full link from origin and Boolean value for checkbox
(pre-1.6)
We can only access DOM elements with prop other then it gives undefined
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.0/jquery.min.js"></script>
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>prop demo</title>
<style>
p {
margin: 20px 0 0;
}
b {
color: blue;
}
</style>
</head>
<body>
<input id="check1" type="checkbox" checked="checked">
<label for="check1">Check me</label>
<p></p>
<script>
$("input").change(function() {
var $input = $(this);
$("p").html(
".attr( \"checked\" ): <b>" + $input.attr("checked") + "</b><br>" +
".prop( \"checked\" ): <b>" + $input.prop("checked") + "</b><br>" +
".is( \":checked\" ): <b>" + $input.is(":checked")) + "</b>";
}).change();
</script>
</body>
</html>
There are few more considerations in prop() vs attr():
selectedIndex, tagName, nodeName, nodeType, ownerDocument, defaultChecked, and defaultSelected..etc should be retrieved and set with the .prop() method. These do not have corresponding attributes and are only properties.
For input type checkbox
.attr('checked') //returns checked
.prop('checked') //returns true
.is(':checked') //returns true
prop method returns Boolean value for checked, selected, disabled,
readOnly..etc while attr returns defined string. So, you can directly
use .prop(‘checked’) in if condition.
.attr() calls .prop() internally so .attr() method will be slightly
slower than accessing them directly through .prop().
Gary Hole answer is very relevant to solve the problem if the code is written in such way
obj.prop("style","border:1px red solid;")
Since the prop function return CSSStyleDeclaration object, above code will not working properly in some browser(tested with IE8 with Chrome Frame Plugin in my case).
Thus changing it into following code
obj.prop("style").cssText = "border:1px red solid;"
solved the problem.