We Keep Coding

Use JavaScript to Get SelectedValue ASP.NET RadiobuttonList

I have the following radio button list on an .aspx page:
<asp:RadioButtonList ID="rbList" runat="server">
<asp:ListItem Text="I accept" Value="accept" />
<asp:ListItem Text="I decline" Value="decline" Selected="True" />
</asp:asp:RadioButtonList>
The second radio is selected by default. Is there a way for me to determine if a user hasn't selected the first option, i.e., "decline" is still selected when they perform an action?
E.g.:
function checkRbList() {
var rbl = document.getElementById(<%= rbList.ClientID %>);
//if "decline" is still selected, alert('You chose to decline')...
}

The following should do the job:
var rbl = document.getElementById("<%= rbList.ClientID %>");
var value = rbl.value;
if(value === 'decline')
alert()

Assuming you have this HTML rendered:
<label>
I accept
<input id="rbList_0" name="rbList" type="radio" value="accept" />
</label>
<label>
I decline
<input id="rbList_1" name="rbList" checked="true" type="radio" value="decline" />
</label>
You can use document.getElementsByName(). Then by using:
document.getElementsByName("rbList") you'll get a NodeList.
This is the function:
function checkRbList() {
var rbl = document.getElementsByName("rbList"), len = rbl.length;
for (var i = 0; i < len; i++) {
if (rbl[i].checked) { // If checked?
return rbl[i].value; // Returns the selected value.
}
}
}
To check if "decline" is still selected:
var targetValue = "decline";
if (checkRbList() === targetValue) {
alert("You chose to decline.");
}
Something like this:
(function() {
var targetValue = "decline";
function checkRbList() {
var rbl = document.getElementsByName("rbList"),
len = rbl.length;
for (var i = 0; i < len; i++) {
if (rbl[i].checked) { // If checked?
return rbl[i].value; // Returns the selected value.
}
}
}
var btnValidate = document.getElementById("btnValidate");
btnValidate.onclick = function() {
console.log(checkRbList()); // Prints the selected value.
if (checkRbList() === targetValue) {
alert("You chose to decline.");
}
};
})();
<label>
I accept
<input id="rbList_0" name="rbList" type="radio" value="accept" />
</label>
<label>
I decline
<input id="rbList_1" name="rbList" checked="true" type="radio" value="decline" />
</label>
<button id="btnValidate" type="button">Validate</button>

I found a way that is working:
var targetValue = "decline";
$('#<% = myBtn.ClientID %>').click(function () {
var items = $("#<% = rbList.ClientID %> input:radio");
for (var i = 0; i < items.length; i++) {
if (items[i].value == targetValue) {
if (items[i].checked) {
alert(items[i].value);
}
}
}
});

How to trigger event on change when function is changing element?

I have a master and a slave set of radio buttons. Setting the master radio sets the slave with JavaScript. Setting the slave only sets the slave.
I've set up an event listener on change for the slave to trigger a function but it's only firing when the user changes it manually, not when it's set by the master. I would like the function to run whenever the slave is set either by user or master.
Are event listeners only set up to listen for user actions? How can I make it work?
I've set up my example here https://jsfiddle.net/taok9edr/2/
HTML -
<form id="master">Master control: <br>
Red:<input id="red" class="color" type="radio" name="color" value="red" checked>
Blue:<input id="blue" class="color" type="radio" name="color" value="blue">
</form>
<form id="slave">Slave: <br>
Red:<input id="redSlave" type="radio" class="colorSlave" name="colorSlave" value="red" checked>
Blue:<input id="blueSlave" type="radio" class="colorSlave" name="colorSlave" value="blue">
</form>
JS-
var color = document.getElementById('master').querySelectorAll('.color');
var colorValue = '';
var master = document.getElementById('master');
var slave = document.getElementById('slave');
function beep() {
for (i = 0; i < color.length; i++) {
if (color[i].checked === true) {
var colorValue = color[i].value;
//console.log(colorValue);
}
}
setSlave(colorValue);
}
function setSlave(value) {
var slaveSelect = slave.querySelectorAll('.colorSlave');
//console.log(slaveSelect);
for (i = 0; i < slaveSelect.length; i++) {
if (slaveSelect[i].checked === true && slaveSelect[i].value === value) {
return;
} else if (slaveSelect[i].checked === true && slaveSelect[i].value !== value) {
//console.log(slaveSelect[i]);
slaveSelect[i].checked = false;
for (i = 0; i < slaveSelect.length; i++) {
if (slaveSelect[i].value === value) {
slaveSelect[i].checked = true;
}
}
}
}
}
function boop() {
console.log('slave has changed');
}
master.addEventListener("change", beep);
slave.addEventListener("change", boop);

getElementByTagName not working

When I click delete button without clicking any checkbox, it should show alert, but in this coding, if first checkbox checked, it doesn't show alert. If second checkbox checked, it show alert.
HTML:
<div id="checkbox">
<input type="CHECKBOX" name="MyCheckbox" class="checkbox" value="This..." >
<input type="CHECKBOX" name="MyCheckbox" class="checkbox" value="This..." >
<input type="CHECKBOX" name="MyCheckbox" class="checkbox" value="This..." >
<input type="CHECKBOX" name="MyCheckbox" class="checkbox" value="This..." >
</div>
<form action="DeleteServer" onsubmit="return checkCheckBoxes(this);">
<input type="SUBMIT" value="Delete!">
</form>
script function:
function checkCheckBoxes() {
var chk = document.getElementById("checkbox").getElementsByTagName("input");
for(var i=0; i<chk.length;i++){
if (document.getElementById("checkbox").getElementsByTagName("input")[i].checked == false)
{
alert ('You didn\'t choose any of the checkboxes!');
return false;
} else {
return true;
}
}
}

getElementsByTagName has an s in it. It is plural. It returns a NodeList not a single Element.
Given your HTML, that NodeList will include 2 separate inputs.
You have to loop over it (as if it was an Array) and test the checked property of each input in turn.

This should solve your problem:
var inputs = document.querySelectorAll('#checkbox input');
is_checked = false;
for(var i = 0; i < inputs.length; i++) {
if(inputs[i].type == 'checkbox' && inputs[i].name == 'MyCheckbox') {
is_checked = inputs[i].checked;
if(is_checked) break;
}
}
if(!is_checked){
alert('You didn\'t choose any of the checkboxes!');
}
Here is a fiddle

function checkCheckBoxes() {
var inputs = document.querySelectorAll('#checkbox input');
is_checked = false;
for(var i = 0; i < inputs.length; i++) {
if(inputs[i].type == 'checkbox') {
is_checked = inputs[i].checked;
if(is_checked) return true;
}
}
if(!is_checked){
alert('You didn\'t choose any of the checkboxes!');
return false;
}
}

Check boxes validation in JavaScript

I have written this script:
function getDays(select){
var selectedString = select.options[select.selectedIndex].value;
if(selectedString == 4)
{
document.getElementById("days_target").style.display = "block";
}else {
document.getElementById("days_target").style.display = "none";
}
}
and in validateForm() function I have this:
var x=document.forms["form1"]["days"].value;
if (x==null || x=="" || x=="Select Days")
{
alert("Oh, you forgot to select days! :)");
return false;
}
var x=document.forms["form1"]["days"].value;
if(x=="4")
{
var cnt = 0;
for (var i = 7; i < document.day.elements.length; i++) {
if (document.day.elements[i].type == 'checkbox') {
if (document.day.elements[i].checked == true) {
cnt++;
}
}
}
if (cnt == 0) {
alert("Atleast 1 day Should be Selected.");
return false;
}
}
HTML like this:
<b>Please enter days required</b><br/>
<select name="days" id="days" style="width:200px;" onchange="getDays(this)">
<option value="Select Days" selected>Select Days</option>
<option value="1">Mon-Fri</option>
<option value="2">Mon-Fri</option>
<option value="3">Mon-Fri</option>
<option value="4">Bespoke Days</option>
</select><br/><br/>
<div id="days_target" style="display:none;">
<b>Select Days</b><br/>
<input type="checkbox" name="day" value="mon"/>Mon <input type="checkbox" name="day" value="tue"/>Tue<br/>
<input type="checkbox" name="day" value="wed"/>Wed <input type="checkbox" name="day" value="thr"/>Thr<br/>
<input type="checkbox" name="day" value="fri"/>Fri <input type="checkbox" name="day" value="sat"/>Sat<br/>
<input type="checkbox" name="day" value="sun"/>Sun<br/><br/>
</div>
If I select Bespoke days then that check boxes appear and if none is checked then I want to display error message "Atleast one day should be selected." How to do this?

You are accessing the checkboxes incorrectly. Forms have elements. Also you start from 7 and count up instead of from 0 and count up or from 6 and count down
var day = document.forms["form1"].day;
for (var i = 0; i < day.length; i++) {
if (day[i].type == 'checkbox') {
if (day[i].checked == true) {
cnt++;
}
}
}
I would do it like this:
Live Demo
var x=document.forms["form1"]["days"].selectedIndex;
if (x<1) {
alert("Please select days");
return false;
}
else if(x==4) { // fifth entry
var checked = false, chk = document.forms["form1"]["day"];
for (var i = 0; i < chk.length; i++) {
if (chk[i].checked) { checked=true; break }
}
if (!checked) {
alert("At least one day should be checked.");
return false;
}
}

The after function in jquery would allow you to easily do this. This would require two steps.
Load Jquery by putting this inside your header tag in the HTML (<head></head>):
<script src="//ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js"></script>
Add javascript in the validation when the condition is not met:
$('#days').after('<label class="error">Atleast one day should be selected.</label.');
Additionally, you will want the error message to go away when the validation rules are met.
$('.error').remove();
You will probably want to adjust the HTML/CSS for displaying purposes, but that should be enough to get you going.

How can I shift-select multiple checkboxes like GMail?

In GMail, the user can click on one checkbox in the email list, hold down the Shift key, and select a second checkbox. The JavaScript will then select/unselect the checkboxes that are between the two checboxes.
I am curious as to how this is done? Is this JQuery or some basic (or complex) JavaScript?

I wrote a self-contained demo that uses jquery:
$(document).ready(function() {
var $chkboxes = $('.chkbox');
var lastChecked = null;
$chkboxes.click(function(e) {
if (!lastChecked) {
lastChecked = this;
return;
}
if (e.shiftKey) {
var start = $chkboxes.index(this);
var end = $chkboxes.index(lastChecked);
$chkboxes.slice(Math.min(start,end), Math.max(start,end)+ 1).prop('checked', lastChecked.checked);
}
lastChecked = this;
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<html>
<head>
</head>
<body>
<input type="checkbox" id="id_chk1" class="chkbox" value="1" />Check 1<br/>
<input type="checkbox" id="id_chk2" class="chkbox" value="2" />Check 2<br/>
<input type="checkbox" id="id_chk3" class="chkbox" value="3" />Check 3<br/>
<input type="checkbox" id="id_chk4" class="chkbox" value="4" />Check 4<br/>
<input type="checkbox" id="id_chk5" class="chkbox" value="5" />Check 5<br/>
<input type="checkbox" id="id_chk6" class="chkbox" value="6" />Check 6<br/>
<input type="checkbox" id="id_chk7" class="chkbox" value="7" />Check 7<br/>
</body>
</html>

This is done through fairly simple javascript.
They keep track of the id of the last checked box and when when another checkbox is checked they use the shiftKey event attribute to see if shift was held while clicking the checkbox. If so they set the checked property of each checkbox in between the two to true.
To determine when a box is checked they probably use an onclick event on the checkboxes

It seems like every answer I can find online is completely dependent on jQuery for this. JQuery adds very little functionality. Here's a quick version that doesn't require any frameworks:
function allow_group_select_checkboxes(checkbox_wrapper_id){
var lastChecked = null;
var checkboxes = document.querySelectorAll('#'+checkbox_wrapper_id+' input[type="checkbox"]');
//I'm attaching an index attribute because it's easy, but you could do this other ways...
for (var i=0;i<checkboxes.length;i++){
checkboxes[i].setAttribute('data-index',i);
}
for (var i=0;i<checkboxes.length;i++){
checkboxes[i].addEventListener("click",function(e){
if(lastChecked && e.shiftKey) {
var i = parseInt(lastChecked.getAttribute('data-index'));
var j = parseInt(this.getAttribute('data-index'));
var check_or_uncheck = this.checked;
var low = i; var high=j;
if (i>j){
var low = j; var high=i;
}
for(var c=0;c<checkboxes.length;c++){
if (low <= c && c <=high){
checkboxes[c].checked = check_or_uncheck;
}
}
}
lastChecked = this;
});
}
}
And then initialize it whenever you need it:
allow_group_select_checkboxes('[id of a wrapper that contains the checkboxes]')

Recently, I wrote a jQuery plugin that provide that feature and more.
After including the plugin you just need to initialize the context of checkboxes with the following code snippet:
$('#table4').checkboxes({ range: true });
Here is the link to the documentation, demo & download: http://rmariuzzo.github.io/checkboxes.js/

Well, the post is quite old but here is a solution I've just come across:
jQuery Field Plug-In

I took the jQuery version from #BC. and transformed it into an ES6 version, since the code is actually pretty elegantly solving the problem, in case anyone still stumbles across this...
function enableGroupSelection( selector ) {
let lastChecked = null;
const checkboxes = Array.from( document.querySelectorAll( selector ) );
checkboxes.forEach( checkbox => checkbox.addEventListener( 'click', event => {
if ( !lastChecked ) {
lastChecked = checkbox;
return;
}
if ( event.shiftKey ) {
const start = checkboxes.indexOf( checkbox );
const end = checkboxes.indexOf( lastChecked );
checkboxes
.slice( Math.min( start, end ), Math.max( start, end ) + 1 )
.forEach( checkbox => checkbox.checked = lastChecked.checked );
}
lastChecked = checkbox;
} ) );
}

Got this solution from http://abcoder.com/javascript/jquery/simple-check-uncheck-all-jquery-function/ (now dead):
JavaScript and HTML code
var NUM_BOXES = 10;
// last checkbox the user clicked
var last = -1;
function check(event) {
// in IE, the event object is a property of the window object
// in Mozilla, event object is passed to event handlers as a parameter
if (!event) { event = window.event }
var num = parseInt(/box\[(\d+)\]/.exec(this.name)[1]);
if (event.shiftKey && last != -1) {
var di = num > last ? 1 : -1;
for (var i = last; i != num; i += di) {
document.forms.boxes['box[' + i + ']'].checked = true;
}
}
last = num;
}
function init() {
for (var i = 0; i < NUM_BOXES; i++) {
document.forms.boxes['box[' + i + ']'].onclick = check;
}
}
<body onload="init()">
<form name="boxes">
<input name="box[0]" type="checkbox">
<input name="box[1]" type="checkbox">
<input name="box[2]" type="checkbox">
<input name="box[3]" type="checkbox">
<input name="box[4]" type="checkbox">
<input name="box[5]" type="checkbox">
<input name="box[6]" type="checkbox">
<input name="box[7]" type="checkbox">
<input name="box[8]" type="checkbox">
<input name="box[9]" type="checkbox">
</form>
</body>

Inspired by the fine answers provided, here's a plain JavaScript version using Array.prototype to coerce nodelists to use array functions, rather than for loops.
(function () { // encapsulating variables with IIFE
var lastcheck = null // no checkboxes clicked yet
// get desired checkboxes
var checkboxes = document.querySelectorAll('div.itemslist input[type=checkbox]')
// loop over checkboxes to add event listener
Array.prototype.forEach.call(checkboxes, function (cbx, idx) {
cbx.addEventListener('click', function (evt) {
// test for shift key, not first checkbox, and not same checkbox
if ( evt.shiftKey && null !== lastcheck && idx !== lastcheck ) {
// get range of checks between last-checkbox and shift-checkbox
// Math.min/max does our sorting for us
Array.prototype.slice.call(checkboxes, Math.min(lastcheck, idx), Math.max(lastcheck, idx))
// and loop over each
.forEach(function (ccbx) {
ccbx.checked = true
})
}
lastcheck = idx // set this checkbox as last-checked for later
})
})
}())
<div class="itemslist">
<input type="checkbox" name="one" value="1">
<input type="checkbox" name="two" value="2">
<input type="checkbox" name="three" value="3">
<input type="checkbox" name="four" value="4">
<input type="checkbox" name="five" value="5">
</div>

I realy liked gyo's example and added some code so it works on all checkboxes with the same name.
I also added a MutationObserver so events are also handled on newly added checkboxes.
$(document).ready(function() {
var previouslyClicked = {};
var rangeEventHandler = function(event) {
if (event.shiftKey && previouslyClicked[this.name] && this != previouslyClicked[this.name]) {
var $checkboxes = $('input[type=checkbox][name='+this.name+']').filter(':visible');
var start = $checkboxes.index( this );
var end = $checkboxes.index( previouslyClicked[this.name] );
// console.log('range', start, end, this, previouslyClicked[this.name]);
$checkboxes.slice(Math.min(start,end), Math.max(start,end)+ 1).prop('checked', previouslyClicked[this.name].checked);
} else {
previouslyClicked[this.name] = this;
}
};
if ("MutationObserver" in window) { // https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver/MutationObserver to refresh on new checkboxes
var mutationCallback = function(mutationList, observer) {
mutationList.forEach((mutation) => {
mutation.addedNodes.forEach((node) => {
if (node.nodeName == 'INPUT' && node.type == 'checkbox') {
$(node).on('click.selectRange', rangeEventHandler);
}
});
});
};
var observer = new MutationObserver(mutationCallback);
observer.observe(document, {
childList: true,
attributes: false, // since name is dynamically read
subtree: true
});
}
$('input[type=checkbox][name]').on('click.selectRange', rangeEventHandler);
});
<html>
<head>
</head>
<body>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div>
First:
<input type="checkbox" name="first">
<input type="checkbox" name="first">
<input type="checkbox" name="first">
<input type="checkbox" name="first">
<input type="checkbox" name="first">
</div>
<div>
Second:
<input type="checkbox" name="second">
<input type="checkbox" name="second">
<input type="checkbox" name="second">
<input type="checkbox" name="second">
<input type="checkbox" name="second">
</div>
</body>
</html>

Found the better solution it works for both select and deselects checkboxes.
Uses a core javascript & Jquery.
$(document).ready(function() {
var $chkboxes = $('.chkbox');
var lastChecked = null;
$chkboxes.click(function(e) {
if(!lastChecked) {
lastChecked = this;
return;
}
if(e.shiftKey) {
var start = $chkboxes.index(this);
var end = $chkboxes.index(lastChecked);
$chkboxes.slice(Math.min(start,end), Math.max(start,end)+ 1).prop('checked', e.target.checked);
}
lastChecked = this;
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<html>
<head>
</head>
<body>
<input type="checkbox" id="id_chk1" class="chkbox" value="1" />Check 1<br/>
<input type="checkbox" id="id_chk2" class="chkbox" value="2" />Check 2<br/>
<input type="checkbox" id="id_chk3" class="chkbox" value="3" />Check 3<br/>
<input type="checkbox" id="id_chk4" class="chkbox" value="4" />Check 4<br/>
<input type="checkbox" id="id_chk5" class="chkbox" value="5" />Check 5<br/>
<input type="checkbox" id="id_chk6" class="chkbox" value="6" />Check 6<br/>
<input type="checkbox" id="id_chk7" class="chkbox" value="7" />Check 7<br/>
</body>
</html>

Here is also another implementation similar to Outlooks multiple selection..
<script type="text/javascript">
function inRange(x, range)
{
return (x >= range[0] && x <= range[1]);
}
$(document).ready(function() {
var $chkboxes = $('.chkbox');
var firstClick = 1;
var lastClick = null;
var range = [];
$chkboxes.click(function(e) {
if(!e.shiftKey && !e.ctrlKey) {
$('#index-' + firstClick).prop('checked', false);
firstClick = $chkboxes.index(this) + 1;
if (firstClick !== null && firstClick !== ($chkboxes.index(this)+1)) {
$('#index-' + firstClick).prop('checked', true);
}
} else if (e.shiftKey) {
lastClick = $chkboxes.index(this) + 1;
if ((firstClick < lastClick) && !inRange(lastClick, range)) {
for (i = firstClick; i < lastClick; i++) {
$('#index-' + i).prop('checked', true);
}
range = [firstClick, lastClick];
} else if ((firstClick > lastClick) && !inRange(lastClick, range)) {
for (i = lastClick; i < firstClick; i++) {
$('#index-' + i).prop('checked', true);
}
range = [lastClick, firstClick];
} else if ((firstClick < lastClick) && inRange(lastClick, range)) {
for (i = 1; i < 100; i++) {
$('#index-' + i).prop('checked', false);
}
for (i = firstClick; i < lastClick; i++) {
$('#index-' + i).prop('checked', true);
}
range = [firstClick, lastClick];
}else if ((firstClick > lastClick) && inRange(lastClick, range)) {
for (i = 1; i < 100; i++) {
$('#index-' + i).prop('checked', false);
}
for (i = lastClick; i < firstClick; i++) {
$('#index-' + i).prop('checked', true);
}
range = [lastClick, firstClick];
}
}
});
});

This is jquery solution that I wrote and use:
All checkboxes have same class named chksel
For faster individual selection a class will carry the order
named chksel_index
Also each checkbox has an attribute named rg that contain same
index
var chksel_last=-1;
$('.chksel').click(function(ev){
if(ev.shiftKey){var i=0;
if(chksel_last >=0){
if($(this).attr('rg') >= chksel_last){
for(i=chksel_last;i<=$(this).attr('rg');i++){$('.chksel_'+i).attr('checked','true')}}
if($(this).attr('rg') <= chksel_last){for(i=$(this).attr('rg');i<=chksel_last;i++){$('.chksel_'+i).attr('checked','true')}}
}
chksel_last=$(this).attr('rg');
}else{chksel_last=$(this).attr('rg');}
})

this solution works for me, also ajax based for DataTables
https://jsfiddle.net/6ouhv7bw/4/
<table id="dataTable">
<tbody>
<tr>
<td><input type="checkbox"></td>
</tr>
<tr>
<td><input type="checkbox"></td>
</tr>
<tr>
<td><input type="checkbox"></td>
</tr>
<tr>
<td><input type="checkbox"></td>
</tr>
</tbody>
</table>
<script>
$(document).ready(function() {
var $chkboxes = $('#dataTable');
var $range = '#dataTable tbody';
var $first = false;
var $indexWrapp = 'tr';
var lastChecked = null;
var $checkboxes = 'input[type="checkbox"]';
$chkboxes.on('click',$checkboxes,function(e) {
if ($first===false) {
lastChecked = $(this).closest($indexWrapp).index();
lastCheckedInput = $(this).prop('checked');
$first=true;
return;
}
if (e.shiftKey) {
var start = lastChecked;
var end = $(this).closest($indexWrapp).index();
$( $range+' '+$indexWrapp).each(function() {
$currIndex=$(this).index();
if( $currIndex>=start && $currIndex<=end ){
$(this).find($checkboxes).prop('checked', lastCheckedInput);
}
})
}
lastCheckedInput = $(this).prop('checked');
lastChecked = $(this).closest($indexWrapp).index();
});
</script>

Here is the Elegant implementation. The idea is to store the first selected input to the lastChecked variable and when the user selects the input field with shiftKey we will run a loop and toggle the inBetween(boolean) and mark all the checkboxes with true value.
Inspired by Wesbos.
let checkboxes = document.querySelectorAll('.wrapper input[type="checkbox"]');
let lastChecked;
function logic(e) {
let inBetween = false;
if (e.shiftKey) {
checkboxes.forEach(checkbox => {
if (checkbox === this || checkbox === lastChecked) {
inBetween = !inBetween;
}
if (inBetween) checkbox.checked = true;
})
}
lastChecked = this;
}
checkboxes.forEach((checkbox, i) => checkbox.addEventListener('click', logic));
.wrapper {
display: flex;
flex-direction: column;
}
<div class="wrapper">
<input type="checkbox" name="one">
<input type="checkbox" name="two">
<input type="checkbox" name="three">
<input type="checkbox" name="four">
<input type="checkbox" name="five">
</div>