Develop Reference

prevent users from entering duplicate entries in text inputs in javascript

I have a DOM in which I want to prevent users from entering duplicate entries in html text input.
The above DOM is not in user's control. It is coming through php.
At this moment, I am focussing only on name="code[]".
This is what I have tried:
$(function(){
$('input[name^="code"]').change(function() {
var $current = $(this);
$('input[name^="code"]').each(function() {
if ($(this).val() == $current.val())
{
alert('Duplicate code Found!');
}
});
});
});
Problem Statement:
I am wondering what changes I should make in javascript code above so that when a duplicate code is entered, alert message "Duplicate code Found" should come up.

you need to add an eventlistener to each item, not an eventlistener for all. Then count inputs with same value, if there's more than 1, it's a duplicate.
Also ignore not-filled inputs.
Check following snippet:
$('input[name*="code"]').each(function() {
$(this).change(function(){
let value = $(this).val();
let count = 0;
$('input[name*="code"]').each(function() {
if ($(this).val() != '' && $(this).val() == value) {
count++;
if (count > 1) alert('duplicate');
}
});
});
$(this).addClass('e');
});
$('#createInput').on('click', function(){
let newInput = document.createElement("input");
newInput.name = 'code[]';
newInput.type = 'text';
newInput.className = 'whatever';
$('#inputGroup').append(newInput);
// repeat the eventlistener again:
$('input[name*="code"]:not(.e').each(function() {
$(this).change(function(){
let value = $(this).val();
let count = 0;
$('input[name*="code"]').each(function() {
if ($(this).val() != '' && $(this).val() == value) {
count++;
if (count > 1) alert('duplicate');
}
});
});
$(this).addClass('e');
});
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="inputGroup">
<input name="code-1" type="text" class="whatever">
<input name="code-2" type="text" class="whatever2">
<input name="code-3" type="text" class="whatever3">
</div>
<input type="button" id="createInput" value="Add input">
Edit:
now works with dynamically created elements. The class 'e' works as flag to not insert 2 event listeners to the same node element, otherwise they will run in cascade, provoking unwanted behaviour.

You can use something like this, that converts the jQuery object to an Array to map the values and find duplicates. I added an option to add a style to the duplicated inputs, so the user knows which ones are duplicated.
function checkDuplicates(){
var codes = $('input[name^="code"]').toArray().map(function(element){
return element.value;
})
var duplicates = codes.some(function(element, index, self){
return element && codes.indexOf(element) !== index;
});
return duplicates;
}
function flagDuplicates(){
var inputs = $('input[name^="code"]').toArray();
var codes = inputs.map(function(element){
return element.value;
});
var duplicates = 0;
codes.forEach(function(element, index){
var duplicate = element && codes.indexOf(element) !== index;
if(duplicate){
inputs[index].style.backgroundColor = "red";
inputs[codes.indexOf(element)].style.backgroundColor = "red";
duplicates++
}
});
return duplicates;
}
$('input[name^="code"]').on("change", function(){
//var duplicates = checkDuplicates(); // use this if you only need to show if there are duplicates, but not highlight which ones
var duplicates = flagDuplicates(); // use this to flag duplicates
if(duplicates){
alert(duplicates+" duplicate code(s)");
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<input name="code-1" type="text">
<input name="code-2" type="text">
<input name="code-3" type="text">

Verify checked checkbox javascript

I'm trying to update in "real time" if I check and uncheck in a list of checkboxs.
With this code:
window.onload = function () {
var input = document.getElementById('listTaxi');
function check() {
var a = input.checked ? "checked" : "not checked";
console.log(a);
}
input.onchange = check;
check();
}
I can do this for one checkbox, but how can I make for multiple checkboxs? A list(div) of checkboxs?
Thanks!!

Assign a class on all checkboxes you want to check if checked or not.
Checkboxes
<input type="checkbox" class="checkboxes" id="checkbox1"/>
<input type="checkbox" class="checkboxes" id="checkbox2"/>
<input type="checkbox" class="checkboxes" id="checkbox3"/>
<input type="checkbox" class="checkboxes" id="checkbox4"/>
Pure Javascript
// getting all checkboxes
var checkboxes = document.getElementsByClassName('checkboxes');
// go through all checkboxes
for(var i = 0; i <= checkboxes.length - 1; i++){
checkboxes[i].onchange = function(e){
alert('Element with id ' + e.target.getAttribute('id') + ' is checked ' +e.target.checked);
}
}
Codepen http://codepen.io/todorutandrei/pen/rLBQOX
Or you can use JQUERY - is it more simple
$('.checkboxes').change(function(){
var item = $(this);
alert('Element with id ' + item.attr('id') + ' is ' + item.is(':checked'));
})
Codepen http://codepen.io/todorutandrei/pen/MegzwR

make them all the same class or give the all the same custom attribute
$(".classname")
$("input[name='customName'])
Jquery will then select all with those
$("#id").change(function() {//if using class name or custom attr loop through the return elements and use a function below to handle the cases
if($(this).is(":checked")) {
//code if checked
}
else{
//code if not checked
}
});

Validating a checkbox after already validating other sections of a form [duplicate]

I have a form with multiple checkboxes and I want to use JavaScript to make sure at least one is checked. This is what I have right now but no matter what is chosen an alert pops up.
JS (wrong)
function valthis(){
if (document.FC.c1.checked) {
alert ("thank you for checking a checkbox")
} else {
alert ("please check a checkbox")
}
}
HTML
<p>Please select at least one Checkbox</p>
<br>
<br>
<form name = "FC">
<input type = "checkbox" name = "c1" value = "c1"/> C1
<br>
<input type = "checkbox" name = "c1" value = "c2"/> C2
<br>
<input type = "checkbox" name = "c1" value = "c3"/> C3
<br>
<input type = "checkbox" name = "c1" value = "c4"/> C4
<br>
</form>
<br>
<br>
<input type = "button" value = "Edit and Report" onClick = "valthisform();">
So what I ended up doing in JS was this:
function valthisform(){
var chkd = document.FC.c1.checked || document.FC.c2.checked||document.FC.c3.checked|| document.FC.c4.checked
if (chkd == true){
} else {
alert ("please check a checkbox")
}
}
I decided to drop the "Thank you" part to fit in with the rest of the assignment. Thank you so much, every ones advice really helped out.

You should avoid having two checkboxes with the same name if you plan to reference them like document.FC.c1. If you have multiple checkboxes named c1 how will the browser know which you are referring to?
Here's a non-jQuery solution to check if any checkboxes on the page are checked.
var checkboxes = document.querySelectorAll('input[type="checkbox"]');
var checkedOne = Array.prototype.slice.call(checkboxes).some(x => x.checked);
You need the Array.prototype.slice.call part to convert the NodeList returned by document.querySelectorAll into an array that you can call some on.

This should work:
function valthisform()
{
var checkboxs=document.getElementsByName("c1");
var okay=false;
for(var i=0,l=checkboxs.length;i<l;i++)
{
if(checkboxs[i].checked)
{
okay=true;
break;
}
}
if(okay)alert("Thank you for checking a checkbox");
else alert("Please check a checkbox");
}
If you have a question about the code, just comment.
I use l=checkboxs.length to improve the performance. See http://www.erichynds.com/javascript/javascript-loop-performance-caching-the-length-property-of-an-array/

I would opt for a more functional approach. Since ES6 we have been given such nice tools to solve our problems, so why not use them.
Let's begin with giving the checkboxes a class so we can round them up very nicely.
I prefer to use a class instead of input[type="checkbox"] because now the solution is more generic and can be used also when you have more groups of checkboxes in your document.
HTML
<input type="checkbox" class="checkbox" value=ck1 /> ck1<br />
<input type="checkbox" class="checkbox" value=ck2 /> ck2<br />
JavaScript
function atLeastOneCheckboxIsChecked(){
const checkboxes = Array.from(document.querySelectorAll(".checkbox"));
return checkboxes.reduce((acc, curr) => acc || curr.checked, false);
}
When called, the function will return false if no checkbox has been checked and true if one or both is.
It works as follows, the reducer function has two arguments, the accumulator (acc) and the current value (curr). For every iteration over the array, the reducer will return true if either the accumulator or the current value is true.
the return value of the previous iteration is the accumulator of the current iteration, therefore, if it ever is true, it will stay true until the end.

Check this.
You can't access form inputs via their name. Use document.getElements methods instead.

Vanilla JS:
var checkboxes = document.getElementsByClassName('activityCheckbox'); // puts all your checkboxes in a variable
function activitiesReset() {
var checkboxesChecked = function () { // if a checkbox is checked, function ends and returns true. If all checkboxes have been iterated through (which means they are all unchecked), returns false.
for (var i = 0; i < checkboxes.length; i++) {
if (checkboxes[i].checked) {
return true;
}
}
return false;
}
error[2].style.display = 'none'; // an array item specific to my project - it's a red label which says 'Please check a checkbox!'. Here its display is set to none, so the initial non-error label is visible instead.
if (submitCounter > 0 && checkboxesChecked() === false) { // if a form submit has been attempted, and if all checkboxes are unchecked
error[2].style.display = 'block'; // red error label is now visible.
}
}
for (var i=0; i<checkboxes.length; i++) { // whenever a checkbox is checked or unchecked, activitiesReset runs.
checkboxes[i].addEventListener('change', activitiesReset);
}
Explanation:
Once a form submit has been attempted, this will update your checkbox section's label to notify the user to check a checkbox if he/she hasn't yet. If no checkboxes are checked, a hidden 'error' label is revealed prompting the user to 'Please check a checkbox!'. If the user checks at least one checkbox, the red label is instantaneously hidden again, revealing the original label. If the user again un-checks all checkboxes, the red label returns in real-time. This is made possible by JavaScript's onchange event (written as .addEventListener('change', function(){});

You can check that atleast one checkbox is checked or not using this simple code. You can also drop your message.
Reference Link
<label class="control-label col-sm-4">Check Box 2</label>
<input type="checkbox" name="checkbox2" id="checkbox2" value=ck1 /> ck1<br />
<input type="checkbox" name="checkbox2" id="checkbox2" value=ck2 /> ck2<br />
<script>
function checkFormData() {
if (!$('input[name=checkbox2]:checked').length > 0) {
document.getElementById("errMessage").innerHTML = "Check Box 2 can not be null";
return false;
}
alert("Success");
return true;
}
</script>

< script type = "text/javascript" src = "js/jquery-1.6.4.min.js" > < / script >
< script type = "text/javascript" >
function checkSelectedAtleastOne(clsName) {
if (selectedValue == "select")
return false;
var i = 0;
$("." + clsName).each(function () {
if ($(this).is(':checked')) {
i = 1;
}
});
if (i == 0) {
alert("Please select atleast one users");
return false;
} else if (i == 1) {
return true;
}
return true;
}
$(document).ready(function () {
$('#chkSearchAll').click(function () {
var checked = $(this).is(':checked');
$('.clsChkSearch').each(function () {
var checkBox = $(this);
if (checked) {
checkBox.prop('checked', true);
} else {
checkBox.prop('checked', false);
}
});
});
//for select and deselect 'select all' check box when clicking individual check boxes
$(".clsChkSearch").click(function () {
var i = 0;
$(".clsChkSearch").each(function () {
if ($(this).is(':checked')) {}
else {
i = 1; //unchecked
}
});
if (i == 0) {
$("#chkSearchAll").attr("checked", true)
} else if (i == 1) {
$("#chkSearchAll").attr("checked", false)
}
});
});
< / script >

Prevent user from deselecting last checked checkbox.
jQuery (original answer).
$('input[type="checkbox"][name="chkBx"]').on('change',function(){
var getArrVal = $('input[type="checkbox"][name="chkBx"]:checked').map(function(){
return this.value;
}).toArray();
if(getArrVal.length){
//execute the code
$('#msg').html(getArrVal.toString());
} else {
$(this).prop("checked",true);
$('#msg').html("At least one value must be checked!");
return false;
}
});
UPDATED ANSWER 2019-05-31
Plain JS
let i,
el = document.querySelectorAll('input[type="checkbox"][name="chkBx"]'),
msg = document.getElementById('msg'),
onChange = function(ev){
ev.preventDefault();
let _this = this,
arrVal = Array.prototype.slice.call(
document.querySelectorAll('input[type="checkbox"][name="chkBx"]:checked'))
.map(function(cur){return cur.value});
if(arrVal.length){
msg.innerHTML = JSON.stringify(arrVal);
} else {
_this.checked=true;
msg.innerHTML = "At least one value must be checked!";
}
};
for(i=el.length;i--;){el[i].addEventListener('change',onChange,false);}
<label><input type="checkbox" name="chkBx" value="value1" checked> Value1</label>
<label><input type="checkbox" name="chkBx" value="value2"> Value2</label>
<label><input type="checkbox" name="chkBx" value="value3"> Value3</label>
<div id="msg"></div>

$('input:checkbox[type=checkbox]').on('change',function(){
if($('input:checkbox[type=checkbox]').is(":checked") == true){
$('.removedisable').removeClass('disabled');
}else{
$('.removedisable').addClass('disabled');
});

if(($("#checkboxid1").is(":checked")) || ($("#checkboxid2").is(":checked"))
|| ($("#checkboxid3").is(":checked"))) {
//Your Code here
}
You can use this code to verify that checkbox is checked at least one.
Thanks!!

jquery enable disable link based on checkbox

I need to disable/enable "a.href" links based on checkboxes being checked. I have a list of checkboxes (2 columns). When at least one checkbox in a column "install" is checked, "Install" link should be enabled, otherwise disabled. When at least one checkbox is checked in column "Remove", a link with the same class name should be enabled, otherwise disabled.
I've tried with this but not sure if this is correct, it doesn't work:
function refleshCheckboxes() {
if ($("input:checked").length > 0) {
$("input:checked").each(function(index, e) {
var css = $(e).attr('class').split(' ').slice(-1);
$("div.markActions a").each(function (index, e) {
$(e).removeClass("disablelink").hasClass(css);
});
});
}
else {
$("div.markActions a").addClass("disablelink");
}
}
$("div.markActions a")
- this is where a.href links are (inside this div)
checkboxes have the same class name as the a.href links. So I would like to get the class name of checkbox and match that class with the class of the a.href link.
Checkbox:
<input type="checkbox" value="2" class="checkbox install">
Link:
<a class="iconDiskPlus install disablelink" href="#">Install</a>

I figured it out:
function refleshCheckboxes() {
if ($("input.checkbox:checked").length > 0) {
var arr = new Array(".install", ".uninstalled", ".enabled", ".disabled", ".download", ".remove");
for (i = 0; i < arr.length; i++) {
if ($("input.checkbox:checked").is(arr[i])) {
$(".markActions a" + arr[i]).removeClass("disablelink");
} else {
$(".markActions a" + arr[i]).addClass("disablelink");
}
};
}
else {
$("div.markActions a").addClass("disablelink");
}
}

Try the below one.
​
$(function(){
$('input.install').click(function(){
var install_link = $('a.install');
if($('input.install:checked').length !=0){
install_link.addClass('enablelink').text('install enabled');
}
else{
install_link.addClass('disablelink').text('install disabled');
}
});
});​
Check out js fiddle for demo

You can set an onclick event to a checkbox like this:
<input id="someId" type="checkbox" value="2" class="checkbox install" onclick="myFunction()">
in your js file define a function:
function myFunction(){
var checkBox = document.getElementById("someId");
if(checkBox.checked == true){
//you have to give an id attribute to the object
// which you want to hide
var hideIt = document.getElementById("id");
hideIt.style.visibility = "none";
}
}

too see if checkboxes have been checked javascript

Hallo
How would I go about in checking whether checkBox has been checked in javascript?
I C# it is simple enough
int selected = 0;
for (int loop = 0; loop < chkMeal.CheckedItems.Count; loop++)
{
selected++;
}
if (selected > 1)
{
MessageBox.Show("only one meal allowed", "Halt", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
How could I do a simlar thing with javascript?
kind regards
Arian

For instance, if you give your checkboxes a class you can do something like this:
var myboxes = document.getElementsByClassName('myboxes');
for (var i=0; i<myboxes.length;i++) {
if (myboxes[i].checked) {
alert('Box number '+i+' is checked!');
}
}

Simply put, give your form a unique id attribute. Then, traverse HTMLFormElement.elements and check against HTMLInputElement.checked for a truthy value.
HTML:
<form id="foo" method="post" action="./">
<input type="checkbox" name="check_a" value="foo" />
<input type="checkbox" name="check_b" value="bar" />
<input type="checkbox" name="check_c" value="baz" checked />
</form>
JS:
var foo = document.getElementById("foo"), i = 0, el;
for(i;i<foo.elements.length;i++)
{
el = foo.elements[i];
if(el.nodeType === 1 && el.tagName === "INPUT" && el.type === "checkbox")
{
//element node, is an input element, is a checkbox
if(el.checked)
{
//checkbox is checked
}
}
el = null;
}
Bonus reference:
HTMLFormElement (via DOM Level 2)
HTMLInputElement (via DOM Level 2)

Using a little bit of jQuery:
$(function() {
$('form').submit( function() {
if ($('[name="chkMeal"]:checked').length > 1) {
// show an error
return false; // cancel submit
}
});
});