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How to clone form elements with auto increamented id to all elements

I have a form under a . I want to clone this and append dynamically in another and so on dynamically. Also I need to assign auto incremented id to all form elements too. Apart from pure javascript I can not use any jQuery or any other library.
Here is my HTML
<tr id="repeat">
<td><input type="text" id="fieldName" /></td>
<td>
<select name="fieldType" id="fieldType">
<option value="string">String</option>
</select>
</td>
<td><input type="radio" id="mandatory" name="mandatory" value="true" /><input type="radio" id="mandatory" name="mandatory" value="false" /></td>
<td>Delete Button</td>
</tr>
Here is my JavaScript
var i = 0;
this.view.findById("start").addEventHandler("click", function () {
var original = document.getElementById('repeat');
var clone = original.cloneNode(true);
original.parentNode.appendChild(clone);
})
Presently I can cloned the form elements in <tr id="repeated1"> dynamically and so on, but unable to assign auto incremented id to input box and select box . Also unable to assign auto incremented name to the radio buttons dynamically

You can change Id or another attribute as you want.
but for your code my solution is using querySelectorAll to get element and change it's Id, something like below code, it is tested and works nice:
Based on this HTML design code and JS function:
function MakeElementsWithDifferentId() {
for (var i = 1; i < 10; i++) {
var original = document.getElementById('repeat');
var clone = original.cloneNode(true);
clone.id="repeat"+i;
clone.querySelectorAll('[id="fieldName"]')[0].id ="fieldName"+i;
clone.querySelectorAll('[id="fieldType"]')[0].id ="fieldType"+i;
clone.querySelectorAll('[id="mandatory"]')[0].id ="mandatory"+i;
clone.children[2].children[0].name="mandatoryName"+i; //To change the radio name also
original.parentNode.appendChild(clone);
}
}
MakeElementsWithDifferentId();
<table>
<tr id="repeat">
<td><input type="text" id="fieldName" /></td>
<td>
<select name="fieldType" id="fieldType">
<option value="string">String</option>
</select>
</td>
<td><input type="radio" id="mandatory" name="mandatory" value="true" /> </td>
<td>Delete Button</td>
</tr>
</table>
the MakeElementsWithDifferentId() function make 10 batch elements with different Ids.
the JSFiddle Test
after run you can right click on element that you want and see the Id by inspect element.
Note:
Instead of clone.querySelectorAll('[id="fieldName"]')[0] it's better to get element by querySelector like clone.querySelector('[id="fieldName"]')
Hope will help you.

Automatic multiplication for several row

I'm new on coding, then any help will greatly appreciated.
I'm trying to make automatic multiplication from 2 value. Basically my table looks like this. Multiplication works perfectly on the first row. If I make another row by simply copying this code:
<tr>
<td><input id="box1" type="text" oninput="calculate()" /></td>
<td><input id="box2" type="text" oninput="calculate()" /></td>
<td><input id="result" /></td>
</tr>
then the second row won't work. This may happen because the id on second row exactly same with the first row. But if I change the id, the script won't work either. Would you please show me how to fix it?
EDIT: I use this scrip for multiplication purpose:
function calculate() {
var myBox1 = document.getElementById('box1').value;
var myBox2 = document.getElementById('box2').value;
var result = document.getElementById('result');
var myResult = myBox1 * myBox2;
result.value = myResult;
}

I would bind a single input event handler to the table, which will catch any input events on any of the table cells' input elements. Within the handler event.target will refer to the input element where the event originated, and you can use DOM navigation properties/methods to find the associated table cells in the same row.
Maybe a little something like this, using class instead of id:
document.getElementById("multiplier").addEventListener("input", function(e) {
var row = e.target.parentNode.parentNode
var val1 = row.querySelector(".valOne").value
var val2 = row.querySelector(".valTwo").value
row.querySelector(".result").value = val1 * val2
})
<table id="multiplier">
<tr>
<td><input class="valOne" type="text" /></td>
<td><input class="valTwo" type="text" /></td>
<td><input class="result" /></td>
</tr>
<tr>
<td><input class="valOne" type="text" /></td>
<td><input class="valTwo" type="text" /></td>
<td><input class="result" /></td>
</tr>
<tr>
<td><input class="valOne" type="text" /></td>
<td><input class="valTwo" type="text" /></td>
<td><input class="result" /></td>
</tr>
</table>
Further reading:
.addEventListener() method
.parentNode property
.querySelector() method
It would be better to use e.target.closest("tr") instead of e.target.parentNode.parentNode, but note that the .closest() method isn't supported in IE so you would need to use a polyfill.
Note that the JS that I've shown would need to be in a script element that is after the table (e.g., at the end of the body right before the closing </body> tag), or you'd need to wrap it in a document load or DOMContentLoaded handler.

How to retrieve references from group Checkbox name arrays using JS or jQuery

I have a hard JS/jQuery riddle ! Hard because I couldn't find it on Google nor here, neither now, nor months ago when I was looking for it previously.
A large framework is using checkboxes in a table:
<table class="ListTable">
<tr>
<td><input name="blnChecked[70_20]" type="checkbox" value="1" id="some_unusable_gobbledy_gook" /></td>
<td></td>...
</tr>
<tr>
<td><input name="blnChecked[71_20]" type="checkbox" value="1" id="some_more_unusable_gobbledy_gook" /></td>
<td></td>...
</tr>
<tr>
<td><input name="blnChecked[70_25]" type="checkbox" value="1" id="some_further_unusable_gobbledy_gook" /></td>
<td></td>...
</tr>
</table>
I now need to collect all checkbox name references into an array: 70_20, 71_20 and 70_25 in the above example. Then join them up, and submit them as a URL parameter to a different page (although this joining is not essential to my question).
Question: Using JS/jQuery on the same page, how do I get these references from the name strings in these (checked) checkboxes in an array ?
I prefer not to use regexes (a bit messy, or 'overkill' for such a seeming trivial matter imho), although such a solution is not off my table.
(If someone asks why the table is structured as such: This is not my doing. But I can see that when such a form, in which this table is submitted to a PHP page, the PHP stores all such checkboxes into a single array, which is very nice, and I wanted to achieve a similar effect with JS/jQuery.)

A way to create on client side the array is based on using:
.map()
string .replace()
$('#btn').on('click', function(e) {
var retVal = $('table.ListTable :checkbox[name^="blnChecked["]:checked').map(function(idx, ele) {
//
// if the name value has always the same format...
//
return ele.name.replace('blnChecked[', '').replace(']', '');
//
// or....
//
// return ele.name.split('[').pop().replace(']', '');
// return ele.name.substr(11, 5);
//return ele.name.replace(/blnChecked\[(.*?)\]/g, '$1')
}).get();
var param = $.param({'param': retVal.join(',')});
console.log('Array: ' + retVal);
console.log('URL param: ' + param);
})
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table class="ListTable">
<tr>
<td><input name="blnChecked[7125_2355]" type="checkbox" value="1" id="some_unusable_gobbledy_gook" /></td>
<td></td>
</tr>
<tr>
<td><input name="blnChecked[71_20]" type="checkbox" value="1" id="some_more_unusable_gobbledy_gook" /></td>
<td></td>
</tr>
<tr>
<td><input name="blnChecked[70_25]" type="checkbox" value="1" id="some_further_unusable_gobbledy_gook" /></td>
<td></td>
</tr>
</table>
<button type="button" id="btn">Click Me</button>

Using javascript to get a value from html input

I am new to this forum and I want to be able to get a value from my html inputs into javascript. Right now i have this code:
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>PWS</title>
</head>
<body bgcolor="#009933" text="#FFFFFF">
<H1 align="center">PWS Julia en Sophie</H1>
<hr>
<br>
<strong>DOUCHE</strong>
<table>
<tr>
<td>Temperatuur</td>
<td><input type="text" name="dtemp" onClick="calculateTotal()" /></td>
</tr>
<tr>
<td>Tijd</td>
<td><input type="text" name="dtijd" onClick="calculateTotal()" /></td>
</tr>
<tr>
<td>Hoe vaak per week</td>
<td><input type="text" name="dfreq" onClick="calculateTotal()" /></td>
</tr>
</table>
<br>
<strong>BAD</strong>
<table>
<tr>
<td>Temperatuur</td>
<td><input type="text" name="btemp" onClick="calculateTotal()" /></td>
</tr>
</tr>
<tr>
<td>Hoe vaak per week</td>
<td><input type="text" name="bfreq" onClick="calculateTotal()" /></td>
</tr>
</table>
<script type="text/javascript">
var dTemp = document.getElementsByName("dtemp").value;
document.write(dTemp);
</script>
obviously, its not working. Because the dTemp value stays undefined.
Can anyone help me, thanks in advance,
Bob

document.getElementsByName returns an array, so you have to reference the position of the element:
var dTemp = document.getElementsByName("dtemp")[0].value;
I would also recommend giving ID's to your inputs, since it seems that each name is unique in your case, that way you could use document.getElementById

document.getElementsByName("dtemp") will give you array of elements, traverse through one by one and get the value from it.
var elements = document.getElementsByName("dtemp");
var firstValue = elements[0].value;

1) You need to index the result of getElementsByName, as described in other answers; append [0] to document.getElementsByName("dtemp").
2) You can’t use document.write in code that is executed after the page has loaded. It would replace the current document by the written content. Write to an element instead.
3) You have not defined the function calculateTotal at all. Wrap your JavaScript code in a function, e.g.
<div id=result></div>
<script>
function calculateTotal() {
var dTemp = document.getElementsByName("dtemp")[0].value;
document.getElementById('result').innerHTML = dTemp; }
</script>
4) You have a long way to go, since now your code makes no attempt at calculating anything, you should hardly use onclick on an input element to start the calculation (rather, onchange on it, or onclick on a separate button element). You should read a good JavaScript primer, really.

jQuery, Can't get value of textbox

In my code, I can get the object but not the value. How can I get the value of the .cups textbox? Thanks.
HTML:
<tr id="20">
<td class="description">CHEESE,FONTINA</td>
<td><input type="text" class="cups" value=""></td>
<td><input type="checkbox" class="breakfast"></td>
<td><input type="checkbox" class="lunch"></td>
<td><input type="checkbox" class="dinner"></td>
<td><input type="checkbox" class="snack"></td>
<td><input type="checkbox" class="favorites"></td>
<td><label class="addFood"><input type="button" class="input_text_custom input_button" value="Add"></label></td>
</tr>
JS:
$(document).ready(function () {
$('.addFood').click(function () {
var tr = $(this).parents('tr');
var foodId = tr.attr('id'); // works
var servings = tr.children('.cups'); // returns [object Object]
var servings = tr.children('.cups').val(); // returns undefined
alert(servings);
});
});

The <input> is a grandchild of <tr>, not a child, so it won't be selected by .children and you get a jQuery object which has no members when you try it (this is akin to an empty array).
Use .find instead, that operates on descendants.

I always find that it is best to be as verbose as you can with jQuery selectors. Especially when it comes to classes as there can be more than one element or types of elements that could be matched. Id's are unique so tr#20 is overkill (IMO).
I would use something like this -
var cupsValue = $("#20 input.cups").val();
If you still want to use a derivative of your code, I would also suggest that you use closest() and not parents() (unless there is something I'm missing from your markup). You are only looking for one parent object, the closest tr that is a parent of the current element.