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jQuery - serializeArray() is not getting the value of the checked checkbox

I have a checkbox in a form that acts as a flag.
In order to do it, I added a hidden input element so that if the checkbox is not checked, something will still be saved
<form action="">
...
<input type="hidden" name="foo" value="no" />
<input type="checkbox" name="foo" value="yes">
...
</form>
The problem I am having is that when I
check the checkbox
then run jQuery.serializeArray() on the form
the value set for the foo element is "no"
Object { name="foo", value="no"}
Shouldn't serializeArray() emulate browser behaviour? If so, shouldn't it return "yes" if checkbox is checked?
I am using jQuery v1.10.2

In a short word: No. The serializeArray method only returns the checkbox in the case it is checked. Thus, it will ignore it as long as it remains unchecked.
In case you checked it, though, it wiill return the value of your input directly.
Check out the demo at http://api.jquery.com/serializearray/ .

Using serializeArray on a form with multiple inputs of the same name returns more than one object for each element (if checked). This means that the following HTML will return the following object. So the data in question is there and is available. Because of this I'm assuming that you're attempting to either manipulate the data to be in 1 object or you're posting it to a server which is only taking into account the data from the first value with that key. You just need to make sure that any checkbox element takes precedence.
Returned Object:
[
{
name:"foo",
value:"no"
},
{
name:"foo2",
value:"no"
},
{
name:"foo2",
value:"yes"
}
]
HTML:
<form>
<input type="hidden" name="foo" value="no" />
<input type="checkbox" name="foo" value="yes" />
<input type="hidden" name="foo2" value="no" />
<input type="checkbox" name="foo2" value="yes" checked />
</form>
JS:
console.log($('form').serializeArray());
DEMO
Another way you can do this is get rid of the hidden fields and before you submit the form go through each unchecked checkbox and check if there is any data in the serializeArray with the same name. If not just add it in there as a off.
$('#submit').on('click', function(){
var arr = $('form').serializeArray(),
names = (function(){
var n = [],
l = arr.length - 1;
for(; l>=0; l--){
n.push(arr[l].name);
}
return n;
})();
$('input[type="checkbox"]:not(:checked)').each(function(){
if($.inArray(this.name, names) === -1){
arr.push({name: this.name, value: 'off'});
}
});
console.log(arr);
});
DEMO

Using the same name for multiple fields is problematic at best and there is no standardized way that front end systems, or back end systems, will handle it.
The only reason to use the same name is if you are trying to pass some kind of a default value, like you are in the case below, where you are doing a simple yes/no.
What you want, to emulate the browser, is serialize method, not the serializeArray.
I added the form to a page -- from my console:
JSON.stringify(f.serializeArray());
"[{"name":"foo","value":"no"}]"
NO checkmark
JSON.stringify(f.serialize());
""foo=no""
Checkmark
JSON.stringify(f.serialize());
""foo=yes&foo=no""
If your back end system gets confused and is picking up the wrong value, reverse the order of your checkmark and hidden element.

FACT: jQuery serializeArray() does not include unchecked checkboxes that probably we DO need them sent to server (no problem for radios though).
SOLUTION: create a new serialize:
//1. `sel` any collection of `form` and/or `input`, `select`, `textarea`
//2. we assign value `1` if not exists to radios and checkboxes
// so that the server will receive `1` instead of `on` when checked
//3. we assign empty value to unchecked checkboxes
function serialize(sel) {
var arr,
tmp,
i,
$nodes = $(sel);
// 1. collect form controls
$nodes = $nodes.map(function(ndx){
var $n = $(this);
if($n.is('form'))
return $n.find('input, select, textarea').get();
return this;
});
// 2. replace empty values of <input>s of type=["checkbox"|"radio"] with 1
// or, we end up with "on" when checked
$nodes.each(function(ndx, el){
if ((el.nodeName.toUpperCase() == 'INPUT') && ((el.type.toUpperCase() == 'CHECKBOX') || (el.type.toUpperCase() == 'RADIO'))){
if((el.value === undefined) || (el.value == ''))
el.value = 1;
}
});
// 3. produce array of objects: {name: "field attribute name", value: "actual field value"}
arr = $nodes.serializeArray();
tmp = [];
for(i = 0; i < arr.length; i++)
tmp.push(arr[i].name);
// 4. include unchecked checkboxes
$nodes.filter('input[type="checkbox"]:not(:checked)').each(function(){
if(tmp.indexOf(this.name) < 0){
arr.push({name: this.name, value: ''});
}
});
return arr;
}
The reason we assigned empty string to unchecked checkboxes is because a checked one will submit it's value to server which is set in html and can be a zero!!!
So, an empty value denotes a unchecked checkbox.

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.0.3/jquery.min.js"></script>
<form url="http://application.localdev/api/v1/register" method="post" id="formReg" accept-charset="utf-8">
<input type="email" placeholder="email" name="email"><br>
<input type="text" placeholder="firstname" name="firstname"><br>
<input type="text" placeholder="lastname" name="lastname"><br>
<input type="number" placeholder="zip_code" name="zip_code"><br>
<input type="checkbox" name="general" value="true"> general<br>
<input type="checkbox" name="marketing" value="true"> marketing<br>
<input type="checkbox" name="survey" value="true"> survey<br>
<button type="submit">save</button>
</form>
<script>
$(document).ready(function() {
$('#formReg').on('submit', function(e){
// validation code here
e.preventDefault();
var values = {};
$.each($('#formReg').serializeArray(), function(i, field) {
values[field.name] = field.value;
});
$('input[type="checkbox"]:not(:checked)').each(function(){
if($.inArray(this.name, values) === -1){
values[this.name] = $(this).prop('checked')
}
});
console.log(values)
});
});
</script>

serializeArray doesn't return unchecked checkbox. I try this instead of serializeArray:
$('input, select, textarea').each(
function(index){
var input = $(this);
alert('Type: ' + input.attr('type') + 'Name: ' + input.attr('name') +
'Value: ' + input.val());
}
);

Iterating through mutiple checkbox values and matching them against a single text input box's value with jQuery

I am trying to check if the value string of a text input field contains any matches that correspond with the values of multiple checkbox inputs. If a checkbox's value is found as a match within the text input's value string, that checkbox should be checked, while any unmatching checkbox should remain unchecked. With the code below, all of the checkboxes show up checked, while only one of the checkbox's value is a match for the text input's value string.
jQuery
$("input[type='checkbox'][name='hello']").each(function(){
var value = $(this).attr('value');
var id = $(this).attr('id');
if ($("input[type='text'][name='goodbye']:contains("+value+")")) {
$("input[id="+id+"]").prop('checked', true);
}
});
HTML
<input type="checkbox" name="hello" id="1" value="1"><label for="1">one</label>
<input type="checkbox" name="hello" id="2" value="2"><label for="2">two</label>
<input type="checkbox" name="hello" id="3" value="3"><label for="3">three</label>
<input type="text" name="goodbye" id="goodbye" value="1">

If you just want to do a text compare the following should work
$("input[type='checkbox'][name='hello']").each(function () {
var value = $(this).val();
if ($('#goodbye').val().indexOf(value) >= 0) {
$(this).prop('checked', true);
}
});
I'm not sure why you were going overly complicated to get the goodbye input, since you had an id and the id is always unique (or you'll have other issues).
$('#goodbye').val()
will give you the value in the input box. using indexOf will return -1 if the value is not found, a number 0 or greater if it is, so we can use that to figure out if the value exists.
example: http://jsfiddle.net/X74NK/1/

Submitting a form using javascript?

I have a gender field in my form.
I have given it the same name, i.e. 'gender', and I have given it the same id, i.e. 'gender'.
Now I want to show what I have selected out of the two options. But with same id, it is not working. I have applied the onclick event to a textbox and I want it so whenever I click on that textbox, I show a javascript alert showing what I have selected, either male or female.
Please help!
gender:<input type="radio" name="gender" id="gender" value="female"/>female
:<input type="radio" name="gender" id="gender" value="male" />male
<input type="text" name="textbox" onclick="check()" />
<script type="text/javascript">
function check()
{
var a=document.getElementById("gender").value;
alert(a);
}
</script>
function addUser() {
//how to check what is the selected radio input
alert(getCheckedRadioId('u_type'));
}
function getCheckedRadioId(name) {
var elements = document.getElementsByName(name);
for (var i=0, len=elements.length; i<len; ++i)
if (elements[i].checked) return elements[i].value;
}
</script>
now this code alerts that what i have choosen but the problem is that i want the alert's value in a variable so that i could send this value to database...so how should i take the alerted value in a variable.....

You might wanna have a look at this:
javascript selected radio
Basically if you had a function that gets the checked radio value by name the problem would be solved. Adopted from the link above:
var selected = '';
var elements = document.getElementsByName('gender');
for (var i = 0, i < elements.length; i++)
{
if (elements[i].checked)
selected = elements[i].value;
}
alert(selected);
Also you might consider using jQuery. It would help a lot in cases like this one.

Your problem is that each element must have a unique Id, and you are giving two elements the same Id. I am not sure which one getElementById() would return. I assume the first.
However, you are quite ok giving multiple elements the same name. Then you could use getElementsByName() to retrieve an array containing the two elements, and you could return whether the element's Checked property is set.

how to call a javascript function on radio button's 'checked' property?

I have N number of radio button groups in the page with auto generated names.
I want to call a javascript function as the value of the checked property. THIS LINE EXCLUDED AFTER EDIT ( Depending on the return value, the radio button needs to be checked or unchecked.)
<input type="radio" name="auto_generated_name" value="some_value" checked="test_check(args);" />
and the javascript function is
function test_check(params) {
if(conditions){
return true;
}
else
return false;
}
But that does not work. Whatever value I assign to 'checked' property, be it any javascript function or any string etc, the radio button becomes checked.
How can I achieve my goal?
EDIT:
<input type="radio" name="auto_generated_name" value="somevalue" onclick="test_check(args)"/>
4 radio buttons make a group. such N radio groups have html class names in this way : button_group_1, button_group_2, button_group_3, button_group_4 etc.
The 'args' need to be these class (i.e. radio button group) names and the corresponding values (from value="1", value="2", value="3" and value="4" ).
Cookies with the class names and values will be created inside the javascript function.
On page refresh, cookies matching with the class names will be checked and depending on the existence of the corresponding cookies, the radio button will be checked or unchecked.
How to achieve the goals/

Assuming you are using jQuery, use the change event: http://api.jquery.com/change/

The checked attribute is simply a boolean value to indicate whether the radio button should be checked, it cannot contain script, or a reference to a scripting function. Any value in the attribute will cause the radio button to be checked.
Without knowing what mechanism you are using to check each radio button - I can see an args variable but don't know what type this is - it's going to be tricky to write some code for you.
If you can make args into an array of values, then something along the lines of the following should work for you:
var args = new Array(true,false,true)
$.each(args, function(index, value) {
$("INPUT[type=radio]").eq(index).attr("checked", value)
});
Here's a fiddle to show what I mean more clearly

check this output, valid args is 'aa'.
http://jsfiddle.net/X7rcC/1
html:
<input type="radio" name="auto_generated_name" value="some_value1" checked="bb" />
js:
$(function() {
var radios = $("input[type='radio']");
$.each(radios, function(index, value){
var args = value.attributes[1].nodeValue;
test_check(args, value);
})
});
function test_check(params, value){
if(params == "aa"){
$(value).attr("checked",true);
}else
$(value).attr("checked",false);
}

try this:
Here I user a custom attribute to input named groupname. In OP's case groupname="<?php echo $radio_button_group_name; ?>". Then checking the value of this attribute OP can assign checked attribute value.
<input type="radio" name="r1" groupname="gr1"/>
<input type="radio" name="r2" groupname="gr2"/>
$('input:radio').each(function() {
if ($(this).attr('groupname') == 'gr1') {
$(this).attr('checked', true);
} else {
$(this).attr('checked', false);
}
});

Your question really boils down to:
How can I set the value of a checkbox when the page first loads? (Using a parameter stored with the checkbox)
The key insights are:
you can't store a function inside a parameter and expect it to automatically evaluate on load
you can store the data about an object inside data- properties
you can set the value of objects on page load in jQuery using the $(document).ready() event
.
<script type="text/javascript">
$(document).ready( function() { // this code runs when the page is first loaded
var radios = $("input[type='radio']"); // find all of your radio buttons
$.each(radios, function(){
var radio = $(this);
var param = radio.attr('data-param'); // retrieve the param from the object
radio.attr('checked', test_check(param) ); // set the value of the radio button
})
});
function test_check(params) {
if(conditions){
return 'checked';
}
else
return '';
}
</script>

You cannot use a checked attribute this way, because anything as the value will be the same as checked=true Even just checked checks a radio button. What you should do is use a custom attribute which will create the checked attribute:
<input type="radio" name="auto_generated_name" value="some_value" needs_check="param">
<script>
// Do test_check on param for each input
$('input:radio').each(function()
{
var radio = $(this);
var param = radio.attr('needs_check');
var condition = test_check(param);
radio.attr('checked', condition);
});
function test_check(param)
{
return true or false based on param
}
</script>

I was facing same problem and my conclusion is that don't use " " to contain a function.
Correct:
<input type="radio" name="im" id="b1" onclick=alert("hello"); />
Incorrect:
<input type="radio" name="im" id="b1" onclick="alert("hello");" />

JavaScript function checked if a radio button is selected

<label for="Merital Status">Marital Status:</label>
<input type="radio" title="Marital Status" name="Marital_Status" id="Marital Status" value="Single"/>Single
<input type="radio" title="Marital Status" name="Marital_Status" value="Married"/>Married
<input type="radio" title="Marital Status" name="Marital_Status" value="Divorced"/>Divorced
And I want to write a JavaScript function that checks whether a radi button named "Merital_Status" is selected. I represent the function that I wrote for this purpose. The function gets as an argument the element id and returnes boolen:
function radio_button_checker(elemId)
{
var radios = document.getElementsByTagName(elemId);
var value = false;
for (var i = 0; i < radios.length; i++)
{
if (radios[i].checked)
{
value = true;
break;
}
}
return value;
}
And I invoke this function like this:
if (radio_button_checker('Marital_Status') == false)
{
alert('Please fill in your Merital Status!');
return false;
}
But it does not work. Please tell me how to modify my function in order to check if radiobutton is checked.

What you are doing is looking for an element with the tag name "Merital_Status". Replace document.getElementsByTagName with document.getElementsByName and it should work.

You are mixing ID's and NAME's.
Your radio button "set" needs to all have the same name (which you have), and if you need to refer to them individually by id, then you'll need to add an id to the last two (currently not set... and not required if you apply the labels to each individual option). You will want the label tags for each radio button as it improves the usability by allowing the user to click on the word not just the small radio button.
Marital Status:
<label><input type="radio" name="Marital_Status" value="Single"/>Single</label>
<label><input type="radio" name="Marital_Status" value="Married"/>Married</label>
<label><input type="radio" name="Marital_Status" value="Divorced"/>Divorced</label>
However when you test... you want to see that at least 1 radio in the set is checked. You can do this with:
function radioButtonChecker(fieldNAME){
var radioSet = document.forms[0].elements[fieldName];
for(var i=0;i<radioSet.length;i++){
if(radioSet[i].checked){
return true;
}
}
return false;
}
There are a few presumptions made here.
You always have more than 1 radio button in the set
Your form is the 1st (index 0) form... if not you'll need to adjust the radioSet lookup