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The radio inputs from my html are not interacting well with my if statements in javascript [duplicate]

I’m having some strange problem with my JS program. I had this working properly but for some reason it’s no longer working. I just want to find the value of the radio button (which one is selected) and return it to a variable. For some reason it keeps returning undefined.
Here is my code:
function findSelection(field) {
var test = 'document.theForm.' + field;
var sizes = test;
alert(sizes);
for (i=0; i < sizes.length; i++) {
if (sizes[i].checked==true) {
alert(sizes[i].value + ' you got a value');
return sizes[i].value;
}
}
}
submitForm:
function submitForm() {
var genderS = findSelection("genderS");
alert(genderS);
}
HTML:
<form action="#n" name="theForm">
<label for="gender">Gender: </label>
<input type="radio" name="genderS" value="1" checked> Male
<input type="radio" name="genderS" value="0" > Female<br><br>
Search
</form>

This works with any explorer.
document.querySelector('input[name="genderS"]:checked').value;
This is a simple way to get the value of any input type.
You also do not need to include jQuery path.

You can do something like this:
var radios = document.getElementsByName('genderS');
for (var i = 0, length = radios.length; i < length; i++) {
if (radios[i].checked) {
// do whatever you want with the checked radio
alert(radios[i].value);
// only one radio can be logically checked, don't check the rest
break;
}
}
<label for="gender">Gender: </label>
<input type="radio" name="genderS" value="1" checked="checked">Male</input>
<input type="radio" name="genderS" value="0">Female</input>
jsfiddle
Edit: Thanks HATCHA and jpsetung for your edit suggestions.

document.forms.your-form-name.elements.radio-button-name.value

Since jQuery 1.8, the correct syntax for the query is
$('input[name="genderS"]:checked').val();
Not $('input[#name="genderS"]:checked').val(); anymore, which was working in jQuery 1.7 (with the #).

ECMAScript 6 version
let genderS = Array.from(document.getElementsByName("genderS")).find(r => r.checked).value;

Here's a nice way to get the checked radio button's value with plain JavaScript:
const form = document.forms.demo;
const checked = form.querySelector('input[name=characters]:checked');
// log out the value from the :checked radio
console.log(checked.value);
Source: https://ultimatecourses.com/blog/get-value-checked-radio-buttons
Using this HTML:
<form name="demo">
<label>
Mario
<input type="radio" value="mario" name="characters" checked>
</label>
<label>
Luigi
<input type="radio" value="luigi" name="characters">
</label>
<label>
Toad
<input type="radio" value="toad" name="characters">
</label>
</form>
You could also use Array Find the checked property to find the checked item:
Array.from(form.elements.characters).find(radio => radio.checked);

In case someone was looking for an answer and landed here like me, from Chrome 34 and Firefox 33 you can do the following:
var form = document.theForm;
var radios = form.elements['genderS'];
alert(radios.value);
or simpler:
alert(document.theForm.genderS.value);
refrence: https://developer.mozilla.org/en-US/docs/Web/API/RadioNodeList/value

Edit:
As said by Chips_100 you should use :
var sizes = document.theForm[field];
directly without using the test variable.
Old answer:
Shouldn't you eval like this ?
var sizes = eval(test);
I don't know how that works, but to me you're only copying a string.

Try this
function findSelection(field) {
var test = document.getElementsByName(field);
var sizes = test.length;
alert(sizes);
for (i=0; i < sizes; i++) {
if (test[i].checked==true) {
alert(test[i].value + ' you got a value');
return test[i].value;
}
}
}
function submitForm() {
var genderS = findSelection("genderS");
alert(genderS);
return false;
}
A fiddle here.

This is pure JavaScript, based on the answer by #Fontas but with safety code to return an empty string (and avoid a TypeError) if there isn't a selected radio button:
var genderSRadio = document.querySelector("input[name=genderS]:checked");
var genderSValue = genderSRadio ? genderSRadio.value : "";
The code breaks down like this:
Line 1: get a reference to the control that (a) is an <input> type, (b) has a name attribute of genderS, and (c) is checked.
Line 2: If there is such a control, return its value. If there isn't, return an empty string. The genderSRadio variable is truthy if Line 1 finds the control and null/falsey if it doesn't.
For JQuery, use #jbabey's answer, and note that if there isn't a selected radio button it will return undefined.

First, shoutout to ashraf aaref, who's answer I would like to expand a little.
As MDN Web Docs suggest, using RadioNodeList is the preferred way to go:
// Get the form
const form = document.forms[0];
// Get the form's radio buttons
const radios = form.elements['color'];
// You can also easily get the selected value
console.log(radios.value);
// Set the "red" option as the value, i.e. select it
radios.value = 'red';
One might however also select the form via querySelector, which works fine too:
const form = document.querySelector('form[name="somename"]')
However, selecting the radios directly will not work, because it returns a simple NodeList.
document.querySelectorAll('input[name="color"]')
// Returns: NodeList [ input, input ]
While selecting the form first returns a RadioNodeList
document.forms[0].elements['color']
// document.forms[0].color # Shortcut variant
// document.forms[0].elements['complex[naming]'] # Note: shortcuts do not work well with complex field names, thus `elements` for a more programmatic aproach
// Returns: RadioNodeList { 0: input, 1: input, value: "red", length: 2 }
This is why you have to select the form first and then call the elements Method. Aside from all the input Nodes, the RadioNodeList also includes a property value, which enables this simple manipulation.
Reference: https://developer.mozilla.org/en-US/docs/Web/API/RadioNodeList/value

Here is an Example for Radios where no Checked="checked" attribute is used
function test() {
var radios = document.getElementsByName("radiotest");
var found = 1;
for (var i = 0; i < radios.length; i++) {
if (radios[i].checked) {
alert(radios[i].value);
found = 0;
break;
}
}
if(found == 1)
{
alert("Please Select Radio");
}
}
DEMO : http://jsfiddle.net/ipsjolly/hgdWp/2/ [Click Find without selecting any Radio]
Source (from my blog): http://bloggerplugnplay.blogspot.in/2013/01/validateget-checked-radio-value-in.html

Putting Ed Gibbs' answer into a general function:
function findSelection(rad_name) {
const rad_val = document.querySelector('input[name=' + rad_name + ']:checked');
return (rad_val ? rad_val.value : "");
}
Then you can do findSelection("genderS");

lets suppose you need to place different rows of radio buttons in a form, each with separate attribute names ('option1','option2' etc) but the same class name. Perhaps you need them in multiple rows where they will each submit a value based on a scale of 1 to 5 pertaining to a question. you can write your javascript like so:
<script type="text/javascript">
var ratings = document.getElementsByClassName('ratings'); // we access all our radio buttons elements by class name
var radios="";
var i;
for(i=0;i<ratings.length;i++){
ratings[i].onclick=function(){
var result = 0;
radios = document.querySelectorAll("input[class=ratings]:checked");
for(j=0;j<radios.length;j++){
result = result + + radios[j].value;
}
console.log(result);
document.getElementById('overall-average-rating').innerHTML = result; // this row displays your total rating
}
}
</script>
I would also insert the final output into a hidden form element to be submitted together with the form.

I realize this is extremely old, but it can now be done in a single line
function findSelection(name) {
return document.querySelector(`[name="${name}"]:checked`).value
}

I prefer to use a formdata object as it represents the value that should be send if the form was submitted.
Note that it shows a snapshot of the form values. If you change the value, you need to recreate the FormData object. If you want to see the state change of the radio, you need to subscribe to the change event change event demo
Demo:
let formData = new FormData(document.querySelector("form"));
console.log(`The value is: ${formData.get("choice")}`);
<form>
<p>Pizza crust:</p>
<p>
<input type="radio" name="choice" value="regular" >
<label for="choice1id">Regular crust</label>
</p>
<p>
<input type="radio" name="choice" value="deep" checked >
<label for="choice2id">Deep dish</label>
</p>
</form>

If it is possible for you to assign a Id for your form element(), this way can be considered as a safe alternative way (specially when radio group element name is not unique in document):
function findSelection(field) {
var formInputElements = document.getElementById("yourFormId").getElementsByTagName("input");
alert(formInputElements);
for (i=0; i < formInputElements.length; i++) {
if ((formInputElements[i].type == "radio") && (formInputElements[i].name == field) && (formInputElements[i].checked)) {
alert(formInputElements[i].value + ' you got a value');
return formInputElements[i].value;
}
}
}
HTML:
<form action="#n" name="theForm" id="yourFormId">

I like to use brackets to get value from input, its way more clear than using dots.
document.forms['form_name']['input_name'].value;

var value = $('input:radio[name="radiogroupname"]:checked').val();

check radio button with no ID, just name, type, value

I am trying to select some radio button on a webpage using Javascript inside Tampermonkey. For this particular button, there is no element ID, so I'm not really sure how to select them.
There's really no other identifying elements for these buttons that I can see.
Note: There's several radio buttons on this page, and the only unique identifier between them is the "value." There are 12 other buttons, but I want these 3 selected by default after the page loads.
<input name="Offense" type="radio" value="Indifferent">
<input name="Likelihood" type="radio" value="Indifferent">
<input name="Humor" type="radio" value="Indifferent">
So, I tried to catch them all at once with this:
document.getElementByValue("Indifferent").checked = true;
but it's not doing anything, I'm sure I'm missing something.
Thank you!

Using querySelector/querySelectorAll from Selectors API returns a NodeList of matching DOM Nodes. Since it is not an Array, a for-loop is used:
var inputs = document.querySelectorAll('input[value="Indifferent"]');
for (var i = 0; i < inputs.length; i++) {
inputs[i].checked = true;
}
The same in jQuery:
$('input[value="Indifferent"]').attr('checked', true);

// list will contain all the radio buttons
var list = $('input[value="Indifferent"]')
$.each(list, function(index, value) {
alert( index + ": " + value );
});
All the data you need will be in the value object
https://jsfiddle.net/o46rhpwL/
And if you are looking for the checked value in the list
https://jsfiddle.net/z73ah82b/

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.

Validating multiple sets of radio buttons

I have a form with 29 selections of radio button pairs, each with a Yes/No selection.
The names of the selections increment like this for each set: ans1, ans2, ans3... ans29.
Each one have a value of "yes" or "no"
It follows more or less like this:
<input type="radio" id="yes1" name="ans1" value="yes"/>
<input type="radio" id="no1" name="ans1" value="no"/>
I want to write a Javascript function to validate the answers when submitting the form. I was thinking of using array's within a loop, but have no idea how to get the selections into an array.
The obvious long method is a repetitive if(ans1 = yes) {do something} if(ans2=yes){do something}.
I have seen examples of getElementsByName but is not sure how to implement it in a simple loop function to test for each and every iteration.

Using jQuery
$("input:radio:checked").each(function (index) {
var this$ = $(this);
var q = this$.attr('name');
var a = this$.val();
console.log('Question: ' + q + ', answer: ' + a);
});
This snippet selects only checked radio buttons and then prints them to the console. You can do whatever you want from here, q is the name of the question (e.g. ans1) and a is the answer itself (i.e. true of false).
See it in action.

use jquery (http://jquery.com/) like
for(int i = 1; i < 30; ++i)
{
if ($('#yes' + i).val() == 'yes'){ do something }
}

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");" />