I think according to W3 spec, you're supposed to do
<input type="checkbox" checked="checked" />
And
selected="selected"
But, most browsers will accept it you just write "CHECKED" and don't give it a value. So, what if you do include the attribute, are there any values that would be (consistently) considered false?
There are no values that will cause the checkbox to be unchecked. If the checked attribute exists, the checkbox will be checked regardless of what value you set it to.
<input type="checkbox" checked />
<input type="checkbox" checked="" />
<input type="checkbox" checked="checked" />
<input type="checkbox" checked="unchecked" />
<input type="checkbox" checked="true" />
<input type="checkbox" checked="false" />
<input type="checkbox" checked="on" />
<input type="checkbox" checked="off" />
<input type="checkbox" checked="1" />
<input type="checkbox" checked="0" />
<input type="checkbox" checked="yes" />
<input type="checkbox" checked="no" />
<input type="checkbox" checked="y" />
<input type="checkbox" checked="n" />
Renders everything checked in all modern browsers (FF3.6, Chrome 10, IE8).
The checked and selected attributes are allowed only two values, which are a copy of the attribute name and (from HTML 5 onwards) an empty string. Giving any other value is an error.
If you don't want to set the attribute, then the entire attribute must be omitted.
Note that in HTML 4 you may omit everything except the value. HTML 5 changed this to omit everything except the name (which makes no practical difference).
Thus, the complete (aside from variations in cAsE) set of valid representations of the attribute are:
<input ... checked="checked"> <!-- All versions of HTML / XHTML -->
<input ... checked > <!-- Only HTML 4.01 and earlier -->
<input ... checked > <!-- Only HTML 5 and later -->
<input ... checked="" > <!-- Only HTML 5 and later -->
Documents served as text/html (HTML or XHTML) will be fed through a tag soup parser, and the presence of a checked attribute (with any value) will be treated as "This element should be checked". Thus, while invalid, checked="true", checked="yes", and checked="false" will all trigger the checked state.
I've not had any inclination to find out what error recovery mechanisms are in place for XML parsing mode should a different value be given to the attribute, but I would expect that the legacy of HTML and/or simple error recovery would treat it in the same way: If the attribute is there then the element is checked.
(And all the above applies equally to selected as it does to checked.)
No value is considered false, only the absence of the attribute. There are plenty of invalid values though, and some implementations might consider certain invalid values as false.
HTML5 spec
http://www.w3.org/TR/html5/forms.html#attr-input-checked :
The disabled content attribute is a boolean attribute.
http://www.w3.org/TR/html5/infrastructure.html#boolean-attributes :
The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.
If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace.
Conclusion
The following are valid, equivalent and true:
<input type="checkbox" checked />
<input type="checkbox" checked="" />
<input type="checkbox" checked="checked" />
<input type="checkbox" checked="ChEcKeD" />
The following are invalid:
<input type="checkbox" checked="0" />
<input type="checkbox" checked="1" />
<input type="checkbox" checked="false" />
<input type="checkbox" checked="true" />
The absence of the attribute is the only valid syntax for false:
<input type="checkbox" />
Recommendation
If you care about writing valid XHTML, use checked="checked", since <input checked> is invalid and other alternatives are less readable. Else, just use <input checked> as it is shorter.
Actually, the HTML 4.01 spec says that these attributes do not require values. I haven't personally encountered a situation where providing a value rendered these controls as unselected.
Here are the respective links to the spec document for selected and checked.
Edit: Firebug renders the checkbox as checked regardless of any values I put in quotes for the checked attribute (including just typing "checked" with no values whatsoever), and IE 8's Developer Tools forces checked="checked". I'm not sure if any similar tools exist for other browsers that might alter the rendered state of a checkbox, however.
The empty string is false as a rule.
Apparently the empty string is not respected as empty in all browsers and the presence of the checked attribute is taken to mean checked. So the entire attribute must either be present or omitted.
checked attribute can be set in the following way in javascript.
(isOrdered stores a boolean value)
<input checked={isOrdered} type="checkbox"/> Ordered
Related
When I write an input tag with checked property like
<input type="radio" checked="checked" />
this is not working. i was looking at this post and it says checked="true" should be used instead. It really works like that. But why? Any clarification would be appreciated. Thanks
See the specification:
A number of attributes are boolean attributes. The presence of a
boolean attribute on an element represents the true value, and the
absence of the attribute represents the false value.
If the attribute is present, its value must either be the empty string
or a value that is an ASCII case-insensitive match for the attribute's
canonical name, with no leading or trailing whitespace.
The values "true" and "false" are not allowed on boolean attributes.
To represent a false value, the attribute has to be omitted
altogether.
Here is an example of a checkbox that is checked and disabled. The
checked and disabled attributes are the boolean attributes.
<label><input type=checkbox checked name=cheese disabled> Cheese</label>
This could be equivalently written as this:
<label><input type=checkbox checked=checked name=cheese disabled=disabled> Cheese</label>
You can also mix styles; the following is still equivalent:
<label><input type='checkbox' checked name=cheese disabled=""> Cheese</label>
The code you say doesn't work, works:
<input type="radio" checked="checked" />
<input type="radio" />
checked="true" works due to error recovery in browsers, but it is wrong and you should not depend on that behaviour.
Suppose this checkbox snippet:
<input type="checkbox" value="1">Is it worth?</input>
Is there any reason to statically define the value attribute of checkboxes in HTML? What does it mean?
I hope I understand your question right.
The value attribute defines a value which is sent by a POST request (i.e. You have an HTML form submitted to a server).
Now the server gets the name (if defined) and the value.
<form method="post" action="urlofserver">
<input type="checkbox" name="mycheckbox" value="1">Is it worth?</input>
</form>
The server would receive mycheckbox with the value of 1.
in PHP, this POST variable is stored in an array as $_POST['mycheckbox'] which contains 1.
I just wanted to make a comment on Adriano Silva's comment.
In order to get what he describes to work you have to add "[]" at the end of the name attribute, so if we take his example the correct syntax should be:
<input type = "checkbox" name="BrandID[]" value="1">Ford</input>
<input type = "checkbox" name="BrandID[]" value="2">GM</input>
<input type="checkbox" name="BrandId[]" value="3">Volkswagen</input>
Then you use something like: $test = $_POST['BrandID']; (Mind no need for [] after BrandID in the php code).
Which will give you an array of values, the values in the array are the checkboxes that are ticked's values.
Hope this helps! :)
One reason is to use the ease of working with values in the system.
<input type="checkbox" name="BrandId" value="1">Ford</input>
<input type="checkbox" name="BrandId" value="2">GM</input>
<input type="checkbox" name="BrandId" value="3">Volkswagen</input>
When the form is submitted, the data in the value attribute is used as the value of the form input if the checkbox is checked. The default value is "on".
$('form').on('change', update).trigger('change')
function update() {
var form = $(this)
form.find('output').text('→ ' + form.serialize())
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form>
<input type="checkbox" name="foo">
<output></output>
</form>
<form>
<input type="checkbox" name="foo" checked>
<output></output>
</form>
<form>
<input type="checkbox" name="foo" value="1" checked>
<output></output>
</form>
<form>
<input type="checkbox" name="foo" value="bananas" checked>
<output></output>
</form>
For the sake of a quick glance answer, from MDN
when a form is submitted, only checkboxes which are currently checked are submitted to the server, and the reported value is the value of the value attribute
It can be confusing because seeing something like
<input type='checkbox' name='activated' value='1'> might lead one to believe that the 1 means true and it will be treated as though it is checked, which is false. The checked attribute itself also only determines if the checkbox should be checked by default on page load, not whether it is currently checked and thus going to be submitted.
Looked at the HTML spec, but couldn't make heads or tails of it: http://www.w3.org/TR/html5/the-input-element.html#attr-input-checked
What is the correct way to check a checkbox in HTML (not dynamically)?
checked="true"
checked="checked"
What is the correct way to uncheck a checkbox?
<input type="checkbox" /> with no checked attribute
checked="false"
checked="none"
Where to check the HTML specification to check/uncheck a checkbox?
For checked state
Older browsers may need:
<input type="checkbox" checked="checked" />
But nowadays simply do:
<input type="checkbox" checked />
For unchecked state
Remove checked attribute, like:
<input type="checkbox" />
Reference: http://www.w3.org/TR/html-markup/input.checkbox.html#input.checkbox.attrs.checked
According to HTML5 drafts, the checked attribute is a “boolean attribute”, and “The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.” It is the name of the attribute that matters, and suffices. Thus, to make a checkbox initially checked, you use
<input type=checkbox checked>
By default, in the absence of the checked attribute, a checkbox is initially unchecked:
<input type=checkbox>
Keeping things this way keeps them simple, but if you need to conform to XML syntax (i.e. to use HTML5 in XHTML linearization), you cannot use an attribute name alone. Then the allowed (as per HTML5 drafts) values are the empty string and the string checked, case insensitively. Example:
<input type="checkbox" checked="checked" />
<input type="checkbox" checked />
HTML5 does not require attributes to have values
In jQuery:
To check the checkbox:
$("#checkboxid").attr("checked","checked");
To uncheck the checkbox:
$("#checkboxid").removeAttr("checked");
The other answers hint at the solution and point you to documentation that after further digging will get you to this answer. Jukka K. Korpela has the reason this is the correct answer, basically I followed his link and then looked up the jQuery docs to get to that result. Just figured I'd save future people who find this article those extra steps.
you can use autocomplete="off" on parent form, so if you reload your page, checkboxes will not be checked automatically
Complementary answer to Robert's answer http://jsfiddle.net/ak9Sb/ in jQuery
When getting/setting checkbox state, one may encounter these phenomenons:
.trigger("click");
Does check an unchecked checkbox, but do not add the checked attribute.
If you use triggers, do not try to get the state with "checked" attribute.
.attr("checked", "");
Does not uncheck the checkbox...
I'm not entirely sure why this hasn't been mentioned before, but for me, the following works:
To set it to checked:
<input type="checkbox" checked>
To set it to unchecked:
<input type="checkbox" unchecked>
(I was having the problem that checkboxes remained checked after reloading the page. Using unchecked solved my problem, so it might be useful to someone else.)
You can refer to this page at w3schools but basically you could use any of:
<input checked>
<input checked="checked">
<input checked="">
<form name="myForm" method="post">
<p>Activity</p>
skiing: <input type="checkbox" name="activity" value="skiing" checked="yes" /><br />
skating: <input type="checkbox" name="activity" value="skating" /><br />
running: <input type="checkbox" name="activity" value="running" /><br />
hiking: <input type="checkbox" name="activity" value="hiking" checked="yes" />
</form>
We all know how to form a checkbox input in HTML:
<input name="checkbox_name" id="checkbox_id" type="checkbox">
What I don't know -- what's the technically correct value for a checked checkbox? I've seen these all work:
<input name="checkbox_name" id="checkbox_id" type="checkbox" checked>
<input name="checkbox_name" id="checkbox_id" type="checkbox" checked="on">
<input name="checkbox_name" id="checkbox_id" type="checkbox" checked="yes">
<input name="checkbox_name" id="checkbox_id" type="checkbox" checked="checked">
<input name="checkbox_name" id="checkbox_id" type="checkbox" checked="true">
Is the answer that it doesn't matter? I see no evidence for the answer marked as correct here from the spec itself:
Checkboxes (and radio buttons) are on/off switches that may be toggled
by the user. A switch is "on" when the control element's checked
attribute is set. When a form is submitted, only "on" checkbox
controls can become successful. Several checkboxes in a form may share
the same control name. Thus, for example, checkboxes allow users to
select several values for the same property. The INPUT element is used
to create a checkbox control.
What would a spec writer say is the correct answer? Please provide evidence-based answers.
Strictly speaking, you should put something that makes sense - according to the spec here, the most correct version is:
<input name=name id=id type=checkbox checked=checked>
For HTML, you can also use the empty attribute syntax, checked="", or even simply checked (for stricter XHTML, this is not supported).
Effectively, however, most browsers will support just about any value between the quotes. All of the following will be checked:
<input name=name id=id type=checkbox checked>
<input name=name id=id type=checkbox checked="">
<input name=name id=id type=checkbox checked="yes">
<input name=name id=id type=checkbox checked="blue">
<input name=name id=id type=checkbox checked="false">
And only the following will be unchecked:
<input name=name id=id type=checkbox>
See also this similar question on disabled="disabled".
HTML5 spec:
http://www.w3.org/TR/html5/forms.html#attr-input-checked :
The disabled content attribute is a boolean attribute.
http://www.w3.org/TR/html5/infrastructure.html#boolean-attributes :
The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.
If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace.
Conclusion:
The following are valid, equivalent and true:
<input type="checkbox" checked />
<input type="checkbox" checked="" />
<input type="checkbox" checked="checked" />
<input type="checkbox" checked="ChEcKeD" />
The following are invalid:
<input type="checkbox" checked="0" />
<input type="checkbox" checked="1" />
<input type="checkbox" checked="false" />
<input type="checkbox" checked="true" />
The absence of the attribute is the only valid syntax for false:
<input />
Recommendation
If you care about writing valid XHTML, use checked="checked", since <input checked> is invalid XHTML (but valid HTML) and other alternatives are less readable. Else, just use <input checked> as it is shorter.
<input ... checked />
<input ... checked="checked" />
Those are equally valid. And in JavaScript:
input.checked = true;
input.setAttribute("checked");
input.setAttribute("checked","checked");
you want this i think:
checked='checked'
checked
checked=""
checked="checked"
are equivalent;
according to spec checkbox
'----ⓘ checked = "checked" or "" (empty string) or empty
Specifies that the element represents a selected control.---'
It's pretty crazy town that the only way to make checked false is to omit any values. With Angular 1.x, you can do this:
<input type="radio" ng-checked="false">
which is a lot more sane, if you need to make it unchecked.
I think this may help:
First read all the specs from Microsoft and W3.org.
You'd see that the setting the actual element of a checkbox needs to be done on the ELEMENT PROPERTY, not the UI or attribute.
$('mycheckbox')[0].checked
Secondly, you need to be aware that the checked attribute RETURNS a string "true", "false"Why is this important? Because you need to use the correct Type. A string, not a boolean. This also important when parsing your checkbox.
$('mycheckbox')[0].checked = "true"
if($('mycheckbox')[0].checked === "true"){
//do something
}
You also need to realize that the "checked" ATTRIBUTE is for setting the value of the checkbox initially. This doesn't do much once the element is rendered to the DOM. Picture this working when the webpage loads and is initially parsed.
I'll go with IE's preference on this one: <input type="checkbox" checked="checked"/>
Lastly, the main aspect of confusion for a checkbox is that the checkbox UI element is not the same as the element's property value. They do not correlate directly.
If you work in .net, you'll discover that the user "checking" a checkbox never reflects the actual bool value passed to the controller.
To set the UI, I use both $('mycheckbox').val(true); and $('mycheckbox').attr('checked', 'checked');
In short, for a checked checkbox you need:
Initial DOM: <input type="checkbox" checked="checked">
Element Property: $('mycheckbox')[0].checked = "true";
UI: $('mycheckbox').val(true); and $('mycheckbox').attr('checked', 'checked');
Just like all input's, this one also has a 'value' attribute. If you set the value attribute along with the name attribute, it will send ${name}=${value} in the headers. Let's say we had a form with a bunch of stuff and we wanted the user to decide what roles they have, we could use a checkbox. The easiest way is to set the 'value' attribute which will be passed along to the server. Like this:
<form action="/server" method="post">
<label>Are you a person?</label>
<input type="checkbox" name="my_checkbox" value="is_person">
</form>
The server will receive the following:
my_checkbox=is_person
but only if the checkbox is checked. This would be
my_checkbox=
if it is empty.
This is the exact same with radio inputs.
But.. I have a feeling this isn't what you're asking for... So just encase I'll write another answer below:
If the checked attribute is set to anything (even false) it will be activated, no matter what. The checked attribute doesn't have a specified value, if it's set to anything it will default to 'true' (even if you set it to false).
For example:
<form action="/server" method="post">
<label>Are you a person?</label>
<input type="checkbox" checked="false"> <!--Still checked-->
</form>
Will be checked even though it's set to false.
<form action="/server" method="post">
<label>Are you a person?</label>
<input type="checkbox" checked="asjdiasjiasdjoasi"> <!--Still checked-->
</form>
Doing this will also check it. It doesn't matter -- as long as it's set it will be checked.
Hope this answers your question, the checked attribute will check the input no matter the value of the attribute.
You can test it here: https://battledash-2.github.io/Live-IDE/
or anywhere like repl.it, or locally.
The technically correct value for a checked checkbox is zero (0), and when the checkbox is not checked, it's index is not defined.
Well, to use it i dont think matters (similar to disabled and readonly), personally i use checked="checked" but if you are trying to manipulate them with JavaScript, you use true/false
I seem to recall most (maybe all) attributes in previously versions of HTML (before HTML5) required attributes to have values, like readonly="readonly".
Is this true for HTML5 and the autofocus attribute?
In HTML, you use boolean attributes with or without values as you like.
A boolean, for W3C, like autofocus can be written like that autofocus or autofocus="autofocus" or also autofocus="".
If you don't want autofocus just don't write it.
I think you are confused because XHTML requires values for all attributes: attributes="values".
Here is some information about boolean attribute use in HTML:
http://www.whatwg.org/specs/web-apps/current-work/multipage/common-microsyntaxes.html#boolean-attribute
Quoting the HTML5 spec and expanding a bit on Pekka:
http://www.w3.org/TR/html5/forms.html#autofocusing-a-form-control:-the-autofocus-attribute :
The autofocus attribute is a boolean attribute.
http://www.w3.org/TR/html5/infrastructure.html#boolean-attributes :
The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.
If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace.
Conclusion:
The following are valid, equivalent and true:
<input type="text" autofocus />
<input type="text" autofocus="" />
<input type="text" autofocus="autofocus" />
<input type="text" autofocus="AuToFoCuS" />
The following are invalid:
<input type="text" autofocus="0" />
<input type="text" autofocus="1" />
<input type="text" autofocus="false" />
<input type="text" autofocus="true" />
The absence of the attribute is the only valid syntax for false:
<input type="text"/>
Recommendation
If you care about writing valid XHTML, use autofocus="autofocus", since <input autofocus> is invalid and other alternatives are less readable. Else, just use <input autofocus> as it is shorter.
No, it's enough to specify the attribute itself. It was that way also in HTML 4.
A number of attributes are boolean attributes. The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.
If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace.
Example:
<label><input type=checkbox checked name=cheese disabled> Cheese</label>