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.
Related
I want to get all values from a set of checkboxes via POST - also the ones that return false. For a single checkbox there is a solution here. It's hacky but it does at least not require Javascript. But how about this
<input name="link[]" type="checkbox"/>
<input name="link[]" type="checkbox"/>
...
A similiar solution as the one suggested in the other post would not work, because it keeps iterating:
<input name="link[]" type="hidden"/> <!-- 0 -->
<input name="link[]" type="checkbox"/> <!-- 1 -->
<input name="link[]" type="hidden"/> <!-- 2 -->
<input name="link[]" type="checkbox"/> <!-- 3 -->
...
The one other way I can think of is explicitly giving them indexes
<input name="link[0]" type="hidden"/>
<input name="link[0]" type="checkbox"/>
<input name="link[1]" type="hidden"/>
<input name="link[1]" type="checkbox"/>
<input name="link[2]" type="hidden"/>
<input name="link[2]" type="checkbox"/>
Or you could do this, without using hidden inputs:
<input name="link[0]" type="checkbox"/>
<input name="link[1]" type="checkbox"/>
<input name="link[2]" type="checkbox"/>
Then check for missing array indexes server-side.
When a form is submitted, all the form elements that have a name attribute specified for them submit their name and their value. With most form elements, the value comes from what the user inputs.
When you submit a form that has radio buttons and/or checkboxes in it, only the name/value pairs form the checked checkbox or radio button is submitted. This way, your form processing code doesn't have to sort out which buttons/boxes were checked. A consequence of this however, is that both checkboxes and radio buttons must have a value set for their value attribute. This value is how you will know which button/box was selected (receiving a name/value pair of checkbox4=true doesn't really tell you much.)
In the following code, we will know which checkboxes were checked just by looking at the data submitted to the form's action which checkboxes were checked and what the meaning of those checks were:
<input type="checkbox" name="chkStudent1" value="Mary"> Mary
<input type="checkbox" name="chkStudent2" value="John"> John
<input type="checkbox" name="chkStudent3" value="Joe"> Joe
Now, when the form is submitted, and let's say you check the second checkbox, the name/value pair of chkStudent2=John will be submitted. Your form processing code will know exactly which element was checked and the corresponding data will be available to that code.
I am working on this little project with an online order service for pizzas.
(using Spring Web MVC, Thymeleaf, ...)
Yesterday, someone helped me out adding inputs for selecting an specific amount and size.
<div>
<form th:action="#{/saveOrderAndReload(name=${pizza.name})}" method="post">
<div class="input-group">
<span class="input-group-addon">Bestellmenge (min. 1, max. 10):</span>
<input type="number" name="amount" class="form-control" min="1" max="10" placeholder="1"/>
</div>
<div class="input-group">
<input type="radio" name="size" value="1"> Klein</input>
<input type="radio" name="size" value="2"> Mittel</input>
<input type="radio" name="size" value="3"> Gross</input>
</div>
<div class="form-group">
<div class="form-group">
<input type="submit" class="btn btn-primary btn-success" value="zur Bestellung hinzufuegen"/>
</div>
</div>
</form>
The "amount" field protects the application itself from false input because it only allows integers from 1-10, otherwise the User gets a notification asking for an numeric input.
The radio input where you can select between 3 sizes has 2 problems:
1) The buttons arent among themselfes, they are next to each other.
2) I dont know how to prevent the user from doing no input.
I looked around for quite some time finding the standart html version for this:
<form>
<input type="radio" name="gender" value="male" checked> Male<br>
<input type="radio" name="gender" value="female"> Female<br>
<input type="radio" name="gender" value="other"> Other
</form>
And something like this:
<ul>
<li th:each="ty : ${allTypes}">
<input type="radio" th:field="*{type}" th:value="${ty}" />
<label th:for="${#ids.prev('type')}" th:text="#{${'seedstarter.type.' + ty}}">Wireframe</label>
</li>
</ul>
We didnt learn anything about the second one so I decided to use the standart html. But I does not want to work like that example: It gets errors that this "checked" expression is not allowed, " tag is not closed" and whatnot.
So my questions are:
1) What can I do to make the input look better?
2) How can I set like a placeholder or standart value so the application always gets this input and does not crash?
As you might have realized I am a complete beginner with this type of stuff so be lenient ;)
Answer 1
If you want the change the way the radio buttons are looking, this might help: http://code.stephenmorley.org/html-and-css/styling-checkboxes-and-radio-buttons/.
Some notes and Answer 2
It gets errors that this "checked" expression is not allowed, " tag is
not closed" and whatnot.
Thymeleaf dies not allow attribute minimization. That means that you need to provide a value for each attribute. You just have to use checked="checked" instead of checked.
<form method="post">
<!-- Make sure to always set a value for attributes when using thymeleaf (use checked="checked" instead of checked) -->
<div><input type="radio" name="gender" value="male" checked="checked" />Male</div>
<div><input type="radio" name="gender" value="female" />Female</div>
<div><input type="radio" name="gender" value="other" />Other</div>
</form>
This is actually wrong:
The "amount" field protects the application itself from false input
because it only allows integers from 1-10, otherwise the User gets a
notification asking for an numeric input.
You are only validating on the client side. Clientside validation is okay if you want to give your users feedback even before they submit your form but it is not enough to protect yourself from bad input.
Nathan Long does explain why client side validation is not enough pretty well (JavaScript: client-side vs. server-side validation):
It is very dangerous to trust your UI. Not only can they abuse your
UI, but they may not be using your UI at all, or even a browser. What
if the user manually edits the URL, or runs their own Javascript, or
tweaks their HTTP requests with another tool? What if they send custom
HTTP requests from curl or from a script, for example?
As you are using spring-mvc you should take adventage of it and take a look at the following tutorial: https://spring.io/guides/gs/validating-form-input/.
To provide default values when working with spring-mvc you can just give the field a value:
public class PersonForm {
// this field will have a default value (foo)
// NotNull will ensure that a value is set for this field when validated by spring (however it can be an empty string... take a look at hibernates #NotBlank annotation if you want to prevent empty string or use a regex)
#NotNull
private String gender = "foo";
}
However default values often dont make sense for input[type="text"]. If you want to prodive a placeholder for any input you could just use the html attribute placeholder="the placeholder":
<input type="text" name="name" value="" placeholder="Enter your name" />
I Understand the ins and outs of forms, but say for example I have the following code:
<form method="post" action="urltoserver">
<input type="checkbox" name="mycheckbox" value="1">Question</input>
</form>
Here I have set a value for the $_POST array. However, if I simply want to know if the checkbox is selected or not (ie im not bothered about the returned value), is it feasible/common practice to leave off the value attribute all together? Would it just return true/false in this case?
I'm assuming PHP since you mentioned $_POST; correct me if I'm wrong.
if a checkbox is checked (and there is no value assigned) you should (IIRC) receive an on value back (as unchecked boxes aren't sent with the request). So, if you had:
<form method="POST">
<input type="checkbox" name="foo" /> Foo
<input type="checkbox" name="bar" checked="checked"/> Bar
<input type="checkbox" name="baz" checked="checked"/> Baz
</form>
You'd see:
isset($_POST['foo']) == false
isset($_POST['bar']) == true
isset($_POST['baz']) == true
on the server-side when you went to read the check state.
the easiest thing to do though, if you're learning, is submit it to a page with the following code:
<?php
var_dump($_REQUEST);
That will show you, verbatim, what was submitted (based on the form's populated values). From there you can play with how you want to format the form to receive the values you're expecting.
I need to send a very long form with lots of checkboxes. They're grouped by areas, like this:
<fieldset>
<legend>Whatever1</legend>
<div class="checkbox-list">
<label class="checkbox inline"><input type="checkbox" name="Hobbies" value="Arts"> Arts</label>
<label class="checkbox inline"><input type="checkbox" name="Hobbies" value="Bars"> Bars</label>
<label class="checkbox inline"><input type="checkbox" name="Hobbies" value="Books"> Books</label>
(more items)
</div>
</fieldset>
<fieldset>
<legend>Whatever2</legend>
<div class="checkbox-list">
<label class="checkbox inline"><input type="checkbox" name="Interests" value="Architecture"> Architecture</label>
<label class="checkbox inline"><input type="checkbox" name="Interests" value="Audio"> Audio/vídeo</label>
<label class="checkbox inline"><input type="checkbox" name="Interests" value="Business"> Business</label>
(more items)
</div>
</fieldset>
The form is much longer, but you get the idea.
Using name="Hobbies" value="Arts" my django backend receives all the checkboxes grouped in a Hobbies array, which is very convenient, but I need to know the unchecked checkboxes, too. I know about the hidden input trick, but it's not useful to me, because I use the value field as part of the checkbox grouping.
Any idea about what can I do?
Well, as I guess you already know, there is fundamentally no way of asking the browser which boxes were left unticked. Blame the inventors of HTML forms...
Here are a few simple approaches which don't break your grouping logic:
Re-generate the list of checkboxes which you displayed on your server side. This is preferable in a lot of cases anyway, since it means you're not trusting the data coming back to be exactly what you displayed. (Consider what happens if I use a debugging tool like Firebug to delete one of your checkboxes, or add a new one...)
Include hidden inputs with a corresponding name for each checkbox - "Interests_All", "Hobbies_All", etc - so that you have two arrays of data, one including just the checked items, one including everything displayed.
Use radio buttons instead of check-boxes. Yes, they display differently, but they can have the functionality you want of submitting a Yes/No value, rather than just adding to the array or not.
How about setting a default false value for each checkbox in the backend. If a value has been passed by the browser, you can then change the value to true.
You could add a hidden input field, and on form submit, use jQuery to populate the value of the hidden input with an array containing the values of the unchecked checkboxes:
$("form").on("submit", function(e) {
e.preventDefault();
// Create an array of unchecked Hobbies
var uncheckedValues = [];
$(this).find("input[name='Hobbies']:not(:checked)").each(function() {
uncheckedValues.push(this.value);
});
// Set the uncheckedValues array as hidden input value
$("#your-hidden-input").val(uncheckedValues);
alert($("#your-hidden-input").val());
// Handle the form submission
handleFormSubmit();
});
See DEMO.
I've solved it. The idea was in IMSoP's answer. Here's my solution, maybe it can help someone:
<fieldset>
<legend>Whatever1</legend>
<div class="checkbox-list">
<input type="hidden" name="Hobbies_Arts">
<label class="checkbox inline"><input type="checkbox" name="Hobbies" value="Arts"> Arts</label>
<input type="hidden" name="Hobbies_Bars">
<label class="checkbox inline"><input type="checkbox" name="Hobbies" value="Bars"> Bars</label>
<input type="hidden" name="Hobbies_Books">
<label class="checkbox inline"><input type="checkbox" name="Hobbies" value="Books"> Books</label>
(more items)
</div>
</fieldset>
With that, is very easy to handle the lists in the django side.
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