Develop Reference

Add new select with unqiue name onchange of previous select

I have a job that requires several hundred select elements on a page. I want to show each select dynamically as the previous is changed. I have a working version in which I put all the select elements in the markup, and then used a simple function to hide them all and show only the first. Then on change of each select the next is added.
This works just fine, but is obviously not ideal. I don't want to put 500 select items in the markup and hide them all for no reason, and my JS function would be 1500 lines long. Plus that would make me feel silly.
How can I automate this process with JS?
I do not need each select to have a unique id, but I do need each select to have a unique and incremented name. Is this possible? I have a working fiddle.
HTML:
<select name="select-one" class="hidden" id="one">
<option value="">not this one</option>
<option value="">pick this one</option>
</select>
<select name="select-two" class="hidden" id="two">
<option value="">not this one</option>
<option value="">pick this one</option>
</select>
<select name="select-three" class="hidden" id="three">
<option value="">not this one</option>
<option value="">pick this one</option>
</select>
<select name="select-four" class="hidden" id="four">
<option value="">not this one</option>
<option value="">pick this one</option>
</select>
JS:
$(document).ready(function() {
$('.hidden').hide();
$('#one').show();
$('#one').change(function(){
$('#two').show();
});
$('#two').change(function(){
$('#three').show();
});
$('#three').change(function(){
$('#four').show();
});
// and so forth...
});

HTML:
<select class="hidden" id="one" name='name_0'>
<option value="">not this one</option>
<option value="">pick this one</option>
</select>
jQuery
$('select').on('change', function() {
$('body').append($(this).clone(true))
})
Result:
Note we are using the overload of the clone() method. This means event handlers and data will be copied along with the elements. So whatever event handler you attached to the original select gets cloned.
If you want to increment the name just use a counter and add the attribute after the clone:
cnt=0;
$('select').on('change', function() {
cnt++
$('body').append($(this).clone(true).attr('name', 'name_' + cnt))
})

My solution:
CSS
.hidden {
display: none;
}
JS
const createSelect = index => `
<select name="select-${index}" class="hidden select" data-index=${index}>
<option value="">not this one</option>
<option value="">pick this one</option>
</select>
`;
$(document).ready(function() {
// Generate 100 selects
for (let i = 0; i < 100; i++) {
$("body").append(createSelect(i));
}
// Show first select
$(`.select[data-index='0']`).show();
$('.select').on('change', function() {
// Store index of a select currently changed
const index = parseInt($(this).attr('data-index'), 10);
// Show next select
$(`.select[data-index='${index + 1}']`).show();
});
});

Javascript change input value when select option is selected

I am very new to javascript. So i have a select option and an input field. What i want to achieve is to have the value of the input field change when i select a particular option. This is what i have tried:
First Name: <input type="text" value="colors">
<select name="">
<option>Choose Database Type</option>
<option onclick="myFunction(g)>green</option>
<option onclick="myFunction(r)>red</option>
<option onclick="myFunction(o)>orange</option>
<option onclick="myFunction(b)>black</option>
</select>
<script>
function myFunction(g) {
document.getElementById("myText").value = "green";
}
function myFunction(r) {
document.getElementById("myText").value = "red";
}
function myFunction(o) {
document.getElementById("myText").value = "orange";
}
function myFunction(b) {
document.getElementById("myText").value = "black";
}
</script>

A few things:
You should use the onchange function, rather than onclick on each individual option.
Use a value attribute on each option to store the data, and use an instance of this to assign the change (or event.target)
You have no ID on your text field
You're missing the end quote for your onclick function
<select name="" onchange="myFunction(event)">
<option disabled selected>Choose Database Type</option>
<option value="Green">green</option>
<option value="Red">red</option>
<option value="Orange">orange</option>
<option value="Black">black</option>
</select>
And the function:
function myFunction(e) {
document.getElementById("myText").value = e.target.value
}
And add the ID
<input id="myText" type="text" value="colors">
Fiddle: https://jsfiddle.net/gasjv4hs/

More proper way is to put your JS code in a different .js file and use Jquery as when you go further with your programming this is the proper way.
Your HTML
<input type="text" id="color" name="color">
<select name="" id="changeData">
<option>Choose Database Type</option>
<option data-value="green">green</option>
<option data-value="red">red</option>
<option data-value="orange">orange</option>
<option data-value="black">black</option>
</select>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js">
</script>
Your JS
$(document).ready(function () {
$('#changeData').change(function(){
var color = $(this).val();
$('#color').val(color);
})
});
Also make sure that you have added Jquery Library to your Project. You can either download Jquery and add in your project folder OR also you can use CDN. in this example CDN is used.

I came up with a similar problem. In my case i was trying to change the minimum value of an input based on the value of an option in a select list. I tried to apply the above solutions but nothing worked. So i came with this, which can be applied to problems similar to this
HTML
<input id="colors" type="text" value="">
<select id="select-colors" name="" onchange="myFunction()">
<option disabled selected>Choose Colour</option>
<option value="green">green</option>
<option value="red">red</option>
<option value="orange">orange</option>
<option value="black">black</option>
</select>
JS
function myFunction() {
var x = document.getElementById("select-colors").value;
document.getElementById("colors").value = x;
}
This works by getting the value of the select with id "select-colors" on every change, assigning it into a variable "x" and inserting it into the input value with id "colors". This can be implemented in anyway based on your problem

You create functions with same name multiple times.
Only last one will work.
the variables you pass g,r,o,b are undefined.
Don't add onclick to option add onchange to select.
Make use of HTML5 data-* attribute
function myFunction(element) {
document.getElementById("myText").value = element;
}
First Name: <input type="text" id="myText" value="colors">
<select name="" onchange="myFunction(this.value);">
<option>Choose Database Type</option>
<option data-value="green">green</option>
<option data-value="red">red</option>
<option data-value="orange">orange</option>
<option data-value="black">black</option>
</select>

You can resolve it this way.
` First Name:
<select name="" onchange="myFunction()" id="selectID">
<option>Choose Database Type</option>
<option >green</option>
<option >red</option>
<option >orange</option>
<option >black</option>
</select>
<script>
function myFunction() {
var selectItem = document.getElementByID('selectID').value;
document.getElementByID('yourId').value = sekectItem;
}
</script>

Here's a way to achieve that:
var select = document.getElementById('colorName');
function myFunction(event) {
var color = 'No color selected';
if (select.selectedIndex > 0) {
color = select.item(select.selectedIndex).textContent;
}
document.getElementById('myText').value = color;
}
select.addEventListener('click', myFunction);
myFunction();
First Name: <input type="text" id="myText">
<select id="colorName">
<option>Choose Database Type</option>
<option>green</option>
<option>red</option>
<option>orange</option>
<option>black</option>
</select>

Your code should be like following.
<input type="text" name="color" id="color">
<select name="" id="change_color">
<option>Choose Database Type</option>
<option >green</option>
<option >red</option>
<option >orange</option>
<option >black</option>
</select>
<script type="text/javascript" src="jquery.js"></script>
<script>
$(document).ready(function () {
$('#change_color').change(function(){
var color = ($(this).val());
$('#color').val(color);
})
});
</script>

Here is JS Code that worked for me
var selectYear = document.getElementById('select-year');
selectYear.addEventListener('change', function() {
var selectedYear = document.getElementById('selected-year');
selectedYear.innerHTML = selectYear.value;
});
Select Input ID: select-year
Text ID: selected-year
Code generated from Codex AI :)

how can i store two info on a single select and call them in separate textbox HTML/JS

<span id="s_home_country">
<select name="Home Country" id="home_country">
<option value="Select one" selected="selected">Select one</option>
<option value="h1">Home1</option>
<option value="h2">Home2</option>
<option value="h3">Home3</option>
<option value="h4">Home4</option>
</select>
</span>
and I have another data that i want to incorporate, when Home1 is selected, I want this to show 21-dec into another textbox automatically. and so on..
var Home_country = [
"21-Dec",
"01-Jan",
"01-Jan",
"01-Jan",
];

You could use an object and an event listener.
var home_country = {
"h1":"21-Dec",
"h2":"01-Jan",
"h3":"01-Jan",
"h4":"01-Jan",
};
var selectbox = document.getElementById('home_country');
var textbox = document.getElementById('home_country_date');
selectbox.addEventListener('change', function(e){
textbox.value = home_country[this.value]
})
<span id="s_home_country">
<select name="Home Country" id="home_country">
<option value="Select one" selected="selected">Select one</option>
<option value="h1">Home1</option>
<option value="h2">Home2</option>
<option value="h3">Home3</option>
<option value="h4">Home4</option>
</select>
</span>
<input type="text" id="home_country_date">

Please find below snippet just add another attribute data-attr1 and on change of select list find selected option and get its attribute with name data-attr1 and pass attribute's value to textbox
$("#home_country").on("change",function(){
$(".txtvalue").val($(this).find("option:selected").attr("data-attr1"));
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<span id="s_home_country">
<select name="Home Country" id="home_country">
<option value="Select one" selected="selected">Select one</option>
<option data-attr1="21-Dec" value="h1">Home1</option>
<option data-attr1="01-Dec" value="h2">Home2</option>
<option data-attr1="02-Dec" value="h3">Home3</option>
<option data-attr1="03-Dec" value="h4">Home4</option>
</select>
</span>
<input type="text" class="txtvalue" />

Add an event listener to your select input which outputs the relevant value from your array when an option is selected:
var el = document.getElementById('home_country');
var textbox = document.getElementById('your_textbox_el');
el.addEventListener('change', function(e){
if (e.target.value == 'h1') {
textbox.value = Home_country[0];
} else if (e.target.value == 'some other condition') {
// do something else
}
}

Unless I'm misunderstanding you, you can just put the values of the Home_country array inside the value properties of the options like so:
<span id="s_home_country">
<select name="Home Country" id="home_country">
<option value="Select one" selected="selected">Select one</option>
<option value="21-Dec">Home1</option>
<option value="01-Jan">Home2</option>
<option value="01-Jan">Home3</option>
<option value="01-Jan">Home4</option>
</select>
</span>
Now, when you do get the value of your select element, it will be the value in the array that you gave.

How to use if else statements in select form?

In my registration page, I'm gonna use two drop-down select that one of them should be hidden if its Negative and if its positive new drop-down will open to choose ...
In mysql table I've table as diabetes name with enom
enum('negative', 'insulin', 'drug', 'ndm', 'mody', '')
Here's my code:
<div><label for="diabetes">Diabetes:</label>
<select id="diabetes" name="diabetes">
<option value="negative">Negative</option>
<option value="">Positive</option>
</select>
</div>
<div><label for="diabetestype">Diabetes Type:</label>
<select id="diabetestype" name="diabetestype">
<option value="insulin">Insulin</option>
<option value="drug">Drug</option>
<option value="ndm">NDM</option>
<option value="mody">MODY</option>
</select>
</div>
For example: If Diabetes is negative value is negative as default then Diabetes Type is hidden
and
If Diabetes is positive then Diabetes type will be appeared to choose items.
those values like insulin, drug, mdm, mody should be inserted into this:
value="positive"
How can I make it through java script?
I can't add class or div or span. Is it possible just through JavaScript using ??
Thank you so much

Use jquery, it is comparatively easier.
$(document).ready(function(){
$("#diabetestype").hide();
$("#diabetes").on("change", function(){
var v = $(this).val();
if(v=="positive"){
$("#diabetestype").show();
}else{
$("#diabetestype").hide();
}
});
});
To make this code workable, you need to add value of Positive option also. So instead value="" change it to value="positive".
You can even hide the label also:
$(document).ready(function(){
$("#diabetestype").closest("div").hide();
$("#diabetes").on("change", function(){
var v = $(this).val();
if(v=="positive"){
$("#diabetestype").closest("div").show();
}else{
$("#diabetestype").closest("div").hide();
}
});
});

<div><label for="diabetes">Diabetes:</label>
<select id="diabet" name="diabet" onchange="checkDiabet();">
<option value="negative">Negative</option>
<option value="positive" id="isDiabet">Positive</option>
</select>
</div>
<div id="type" style="display: hidden;">
<label for="diabetestype">Diabetes Type:</label>
<select id="diabetestype" name="diabetestype">
<option value="insulin">Insulin</option>
<option value="drug">Drug</option>
<option value="ndm">NDM</option>
<option value="mody">MODY</option>
</select>
</div>
<script>
function checkDiabet() {
var isDiabet = document.getElementById("isDiabet").selected;
if (isDiabet == true) { document.getElementById("type").removeAttribute("style"); }
else { document.getElementById("type").style.display = "none"; }
}
</script>
First, set the first select to fire the function checkDiabet() by the attribute onchange. Then give the option an id, which needs to be checked, so you can access it easily.
Then, set the second select to display: none This could be done in a CSS header or file, or like in this case inline. (div style=""), also add an id to access it easily. (div id="type")
Now comes the function checkDiabete(). It checks if the select is selected (can be true or false (bool)). Is selected => show (div id="type"), if not, hide this div (and all of it's contents)
(if is already hidden, it then overwrites the (style="display: none;") with (style="display: none;))
That's it! :)

Try this:
function SelectDiabetes() {
var d = document.getElementById("diabetes").value;
var dType = document.getElementById("diabetestypebox");
if(d == "negative")
dType.style.display = "none";
else
dType.style.display = "block";
}
SelectDiabetes();
<div><label for="diabetes">Diabetes:</label>
<select id="diabetes" name="diabetes" onchange="SelectDiabetes(this.value);">
<option value="negative">Negative</option>
<option value="positive">Positive</option>
</select>
</div>
<div id="diabetestypebox"><label for="diabetestype">Diabetes Type:</label>
<select id="diabetestype" name="diabetestype">
<option value="insulin">Insulin</option>
<option value="drug">Drug</option>
<option value="ndm">NDM</option>
<option value="mody">MODY</option>
</select>
</div>

Call a js function onchange of select id diabetes
<div><label for="diabetes">Diabetes:</label>
<select id="diabetes" name="diabetes" onchange="toggleTypes()">
<option value="negative">Negative</option>
<option value="">Positive</option>
</select>
</div>
<div><label for="diabetestype">Diabetes Type:</label>
<select id="diabetestype" style="display:none" name="diabetestype">
<option value="insulin">Insulin</option>
<option value="drug">Drug</option>
<option value="ndm">NDM</option>
<option value="mody">MODY</option>
</select>
</div>
Use the following javascript
function toggleTypes(){
var el=document.getElementById('diabetes');
var medElem=document.getElementById('diabetestype');
if(el.value=='positive') {
medElem.style.display='block';
} else {
medElem.style.display='none';
}
}

Need JavaScript equivalent of jQuery changing the value of a dropdown when the value of a text field changes

I am working on a Formstack form. I need to use Javascript to change the value of a dropdown box to whatever the value being typed into a text field is once a match is made.
<input type="text" id="field35497729" name="field35497729" size="50" value="" class="fsField">
<select id="field35497839" name="field35497839" size="1" class="fsField">
<option value=""> </option>
<option value="CIPSmember">CIPSmember</option>
<option value="TECHCONNEXmember">TECHCONNEXmember</option>
<option value="TCBCpreferred">TCBCpreferred</option>
<option value="TCBCcomp2015">TCBCcomp2015</option>
</select>
So as soon as someone types in CIPSmember into the text field, the dropdown should be selected with the same value. If there is no match, the dropdown has no selection.
I used the following jQuery on jsFiddle, but it is not working on Formstack:
$('#field35497729').keyup( function() {
$("#field35497839").val($('#field35497729').val());
}
);
Here is one Javascript method I am trying on jsFiddle that does not work:
document.getElementByID('field35497729').onkeyup = function() {
document.getElementById('field35497839').value = document.getElementByID('field35497729').value;
};
I checked here, here and maybe 10 other places but I can't get it to work. There are plenty of tutorials on how to get a text field to change when a dropdown selection change, but not nearly as many on the opposite.

misspelled ID in getElementById
missing end bracket on the jQuery version
simplified to use this and $(this)
I am however curious. Perhaps you want an autocomplete instead?
Here are your fixed versions
Plain JS version
window.onload=function() {
document.getElementById('field35497729').onkeyup = function() {
document.getElementById('field35497839').value = this.value;
}
}
<input type="text" id="field35497729" name="field35497729" size="50" value="" class="fsField">
<select id="field35497839" name="field35497839" size="1" class="fsField">
<option value=""> </option>
<option value="CIPSmember">CIPSmember</option>
<option value="TECHCONNEXmember">TECHCONNEXmember</option>
<option value="TCBCpreferred">TCBCpreferred</option>
<option value="TCBCcomp2015">TCBCcomp2015</option>
</select>
jQuery version
$(function() {
$('#field35497729').on("keyup",function() {
$("#field35497839").val($(this).val()); // or (this.value)
})
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<input type="text" id="field35497729" name="field35497729" size="50" value="" class="fsField">
<select id="field35497839" name="field35497839" size="1" class="fsField">
<option value=""> </option>
<option value="CIPSmember">CIPSmember</option>
<option value="TECHCONNEXmember">TECHCONNEXmember</option>
<option value="TCBCpreferred">TCBCpreferred</option>
<option value="TCBCcomp2015">TCBCcomp2015</option>
</select>