Develop Reference

Change date based on select value/month/year

I want to change date based on selected value
$(document).on('change', '.payment_options', function () {
var value = $('#value_select').val();
var data = $('#per_month_year').val();
var d = new Date();
d.setMonth(d.getMonth() + value);
var subs_till = d.toDateString();
if (data == 'month') {
expire_date = subs_till;
} else {
//if data == year, change the membership valid till the value enter: like 2 years, 3 years etc
}
$('#membership_till_date').html(expire_date);
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<label>Choose Value</label>
<select name="" class="form-control payment_options" id="value_select">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
<option value="6">6</option>
<option value="7">7</option>
<option value="8">8</option>
<option value="9">9</option>
<option value="10">10</option>
<option value="11">11</option>
<option value="12">12</option>
</select>
<label>Choose month/year</label>
<select name="" class="form-control payment_options" id="per_month_year">
<option value="month">Month(s)</option>
<option value="year">Year(s)</option>
</select>
<br>
<small>Membership valid from 'Today' to <span id="membership_till_date">"this have to change after choosing value/month-year"</span></small>
But the problem is it gives +5 year in the result, I want to display exactly the data like, if they choose value-data then display "till +5 month form now", "2 years form now", etc in the membership valid sections

When you get the value of a text field, you always get a String back.
If, for example, you choose the number 2 in the value_select field your code will return a String value of "2".
var value = $('#value_select').val();
So you need to convert the String value to an integer, which you can do like this:
var value = parseInt($('#value_select').val());
Your code then works

Javascript take number selected in a drop down and times by 1.09?

I need to create a drop down menu containing numbers,
<select>
<option value="32">32</option>
<option value="33">33</option>
<option value="34">34</option>
<option value="35">35</option>
</select>
and when a number is selected I want the value to be returned in a <p id="returned-value"></p>tag, but times by 1.09. How can I do that with javascript?

See this fiddle
As you can see in the fiddle, the (selected value * 1.9) is shown in the <p> as soon as a value is selected from the <select>. This is done using onchange. The onchange event occurs when the value of an element has been changed.
HTML
<select id="mySelect" onchange="myFunction()">
<option value="0">0</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
<p id="demo">0</p>
JS
function myFunction() {
var x = document.getElementById("mySelect").value;
document.getElementById("demo").innerHTML = "You selected: " + x * 1.9;
}

var value = parseInt(document.getElementByTagName('select').value);
var newValue = value * 1.09;
document.getElementById('returned-value').innerHTML = newValue;

Multiple identical <select> tags where each option can be selected once

I am creating a website where their are 4 identical dropdown menu's, each dropdown menu has got 10 options. But each of those options can only be selected in one of the dropdown menu's.
So for example:
When I select option 1 in this dropdown menu.
<select name="select1">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">2</option>
<option value="4">4</option>
</select>
I can't select it in this one. So it should say disabled in option one.
<select name="select2">
<option value="1" //disabled >1</option>
<option value="2">2</option>
<option value="3">2</option>
<option value="4">4</option>
</select>
I don't know how to do it myself so I would be very glad if someone could help me.

To provide a better user experience, you should disable the items using JavaScript when the user selects something in a drop down. Are you using jQuery by any chance?
You should also enforce it on the server because as a general rule, clients are not to be trusted.

If I understand you correctly, what you are trying to achieve is better done via checkboxes.
Instead of <select> do this:
<input type="checkbox" name="1" value="1">option1<br>
<input type="checkbox" name="2" value="2">option2 <br> ...

The code below does what you are asking. I also made a jsfiddle
It will correctly disable and enable options as options from ANY of the select inputs are changed.
The javascript
<script type="text/javascript">
// *** EDIT THIS ***
var selectIds = new Array('select1', 'select2', 'select3', 'select4'); // all of the select input id values to apply the only one option value anywhere rule against
function process_selection(theObj){
var allSelectedValues = new Array(); // used to store all currently selected values
// == get all of the currently selected values for all the select inputs
for (var x=0; x<selectIds.length; x++){
var v = document.getElementById(selectIds[x]).value; // the value of the selected option for the select input currently being looked at in the loop (selectIds[x])
// if the selected option value is not an empty string ..
if(v!==""){
// store the value of the selected option and it's associated select input id value
allSelectedValues[v] = selectIds[x];
}
}
// == now work on each option within each select input
for (var x=0; x<selectIds.length; x++){
// loop thru all the options of this select input
var optionObj = document.getElementById(selectIds[x]).getElementsByTagName("option");
for (var i = 0; i < optionObj.length; i++) {
var v = optionObj[i].value; // the value of the current option in the iteration
// only worry about option values that are not an empty string ("")
if(v!==""){
if(allSelectedValues[v]){
if(allSelectedValues[v] && allSelectedValues[v] != selectIds[x]){
// disable this option because it is already selected
// and this select input is NOT the one that it is selected in
optionObj[i].disabled = true;
}
}else{
// enable this option because it is not already selected
// in any of the other select inputs
optionObj[i].disabled = false;
}
}
} // end for (option loop)
} // end for (select loop)
} // end func
</script>
The HTML that works with the above
But really the code above will work with any select inputs on your page by editing the one line indicated in the js code above
<select name="select1" id="select1" onchange="process_selection(this)">
<option value="">-- choose one --</option>
<option value="0">0</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
<select name="select2" id="select2" onchange="process_selection(this)">
<option value="">-- choose one --</option>
<option value="0">0</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
<select name="select3" id="select3" onchange="process_selection(this)">
<option value="">-- choose one --</option>
<option value="0">0</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
<select name="select4" id="select4" onchange="process_selection(this)">
<option value="">-- choose one --</option>
<option value="0">0</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>

As others have mentioned, it is a cleaner way to do it in checkboxes. However, just to improve my JavaScript skills, I came up with something that should answer what you asked for:
var boxes, i, disableOthers;
boxes = document.getElementsByTagName('select');
disableOthers = function () {
'use strict';
var i, j, k, selectedValues = [],
options;
for (i = 0; i < boxes.length; i += 1) {
selectedValues.push(boxes[i].value);
for (j = 0; j < boxes.length; j += 1) {
if (boxes[j] !== boxes[i]) {
options = boxes[j].querySelectorAll('option');
for (k = 0; k < options.length; k += 1) {
options[k].disabled = (selectedValues.indexOf(options[k].value) > -1);
}
}
}
}
};
for (i = 0; i < boxes.length; i += 1) {
boxes[i].addEventListener('change', disableOthers, false);
}
See jsFiddle

How to exclude items from a drop down based on another drop down

I have three identical drop downs. I want to select a value from drop1 and have that value excluded from drop2. Then the selections in drop3 should exclude 1 & 2. Any ideas?
<select name="drop1">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
<select name="drop2">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
<select name="drop3">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>

You can use change event and remove selected elements from the dom
$('select[name=drop1]').change(function() {
var drop2 = $('select[name=drop2]').empty().hide();
var exclude = $(this).val();
var size = $(this).children().length;
for (var i=0; i<size; ++i) {
if (i != exclude) {
drop2.append('<option value="' + i + '">' + i + '</option>';
}
}
});
if you have more complex example and you need value based explude you can create a clone.
var clone = $('select[name=drop2]').clone();
$('select[name=drop1]').change(function() {
var copy = clone.clone();
copy.find('option[value=' + $(this).val() + ']').remove().end();
$('select[name=drop2]').replaceWith(copy);
});

Depending on how comfortable you are with PHP, or AJAX you have two solutions.
If you are more comfortable with PHP you could have a user submit the data from one select form and then using if statements like
if $value != '1'{
echo '<option value="1">1</option>';
}
and do that for each field in the second form; then replicate that for the third form.
The smoother looking solution would be using AJAX to use a listener to see when a user clicks a field a java value is set as that field and using a similar "if then show" method on the java-script variable to hide the fields that contain that value in the other forms.
Also one of the easiest solutions would be allowing multiple-selections (Assuming you are ok with the look of using one form & the values between the forms are the same like the example you gave above)... That example being:
<select id="my_num" name="my_num" size="5" multiple="multiple" >
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>

Changing values in dynamically generated html using Jquery

As the title says, I'm wondering if there's a way to change the value of html items that are generated by jquery. Here's the code that I currently have:
the javascript
<script type="text/javascript">
$(document).ready(function() {
$('#months').change(function() {
var currentDate = new Date();
var curentMonth = currentDate.getMonth();
var curentYear = currentDate.getYear();
$(".row:not(:first)").remove();
for (var i = 0; i < this.selectedIndex; i++)
$(".row:first").clone(true).insertAfter(".row:last");
$('#dateDueMonth['+i+']').val(curentMonth + 1);
})
});
</script>
My thought here was that after the row was cloned, I could then change the dropdowns content based upon it's current name, but obviously that's not working, and I've been unable to find a way to "hook" into dynamic html content.
and the base html
<select id="months" name="months">
<option selected value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
<option value="6">6</option>
<option value="7">7</option>
<option value="8">8</option>
<option value="9">9</option>
<option value="10">10</option>
<option value="11">11</option>
<option value="12">12</option>
</select>
</td><div id="showRows"><div class="row" id="row[]"><td class="td_alt"><select id="dateDueMonth[]" name="dateDueMonth[]" >
<option value="0">Select</option>
<option value="1">Jan</option>
<option value="2">Feb</option>
<option value="3">Mar</option>
<option value="4">Apr</option>
<option value="5">May</option>
<option value="6">Jun</option>
<option value="7">Jul</option>
<option selected value="8">Aug</option>
<option value="9">Sep</option>
<option value="10">Oct</option>
<option value="11">Nov</option>
<option value="12">Dec</option>
</select>
<select id="dateDueYear[]" name="dateDueYear[]">
<option value="2005">2005</option>
<option value="2006">2006</option>
<option value="2007">2007</option>
<option value="2008">2008</option>
<option value="2009">2009</option>
<option value="2010">2010</option>
<option selected value="2011">2011</option>
</select>
Now the generation of dynamic html and form submission works great. Gives me the data that I can use for my back end code. However having it so that I can increment the values in the various dropdowns as I see fit would make data entry by the folks using this page a whole lot easier, hence the issue.
To all that reply, thanks for your help with this jquery/JS noob.
EDIT: For this what I want to have is a form that can spawm multiples copies of the first line encased within the showRows div. When this is submitted, I want it to be able to collect that information in arrays for each select/input statement for the rows that are generated. For example if I selected two months, dateDueMonth, dateDueYear, and amount would be arrays in my form that would have two entries each. The current code does this, but by default it has the default elements for the dropdown menus set the same as the row of HTML that it is cloning.

Not sure what you want to do, but it should work like this
$(document).ready(function() {
$('#months').change(function() {
var currentDate = new Date();
var curentMonth = currentDate.getMonth();
var curentYear = currentDate.getYear();
var arr;
$(".row:not(:first)").remove();
for (var i = 0; i < this.selectedIndex; i++)
arr=[$(".row:first").clone(true).insertAfter(".row:last")];
$('#dateDueMonth['+i+']').val(curentMonth + 1); //don't know why its here
arr[0].text("your value"); //apply the index you wanna change
})
});

Are you trying to achieve this kind of markup? Demo
<div id="showRows"><div class="row" id="row[0]"><select id="dateDueMonth[0]" name="dateDueMonth[0]">
<option value="0">Select</option>
...
</select>
<select id="dateDueYear[0]" name="dateDueYear[0]">
<option value="2005">2005</option>
...
</select>
</div><div class="row" id="row[1]"><select id="dateDueMonth[1]" name="dateDueMonth[0]">
<option value="0">Select</option>
...
</select>
<select id="dateDueYear[1]" name="dateDueYear[0]">
<option value="2005">2005</option>
...
</select>
...
This may be what you need. See my demo linked above.
for (var i = 1; i <= this.selectedIndex; i++) {
row = $(".row:first").clone(true)[0];
row.id = "row["+i+"]";
$(row).find("[id^='dateDueMonth']").attr("id","dateDueMonth["+i+"]").val((curentMonth + i) % 12 + 1);
$(row).find("[id^='dateDueYear']").attr("id","dateDueYear["+i+"]");
$(row).insertAfter(".row:last");
}

you cannot use ids as array in JavaScript. if you want, you have to put array index as well when you create element. or else just access the select element as bellow
$(document).ready(function() {
$('#months').change(function() {
var currentDate = new Date();
var curentMonth = currentDate.getMonth();
var curentYear = currentDate.getYear();
$(".row:not(:first)").remove();
for (var i = 0; i < this.selectedIndex; i++) {
$(".row:first").clone(true).insertAfter(".row:last");
$('.row:last select').val(curentMonth + 1);
}
})
});
Working sample