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Multiplication in jQuery dynamically

I am trying to make a multiplication function in jquery where which helps change the default value-based output.
For example - if I type the input#mainInput value then it will change all the inputs value base own his default value * input#mainInput and if the value == 'NaN' it will do dirent funcion.
Please help me how to I make this function in jQuery.
$(document).on('keyup', 'input#mainInput', function() {
thisParentQtyValueBox = $(this).val();
daughtersBoxValueAttr = $("input.input__bom").attr("inputid");
daughtersBoxValue = $("input#daughterInput_" + daughtersBoxValueAttr).val();
$("input#daughterInput_" + daughtersBoxValueAttr).val(thisParentQtyValueBox * daughtersBoxValue);
if ($("input#daughterInput_" + daughtersBoxValueAttr) == 'Nan') {
$("input#daughterInput_" + daughtersBoxValueAttr).val('3' * daughtersBoxValue)
}
});
//If
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<input id="mainInput" type="text" placeholder="Number" />
<br><br>
<input class="input__bom" id="daughterInput_1" type="text" placeholder="value" inputid="1" value="5" /><br/>
<input class="input__bom" id="daughterInput_2" type="text" placeholder="value" inputid="2" value="10" /><br/>
<input class="input__bom" id="daughterInput_3" type="text" placeholder="value" inputid="3" value="15" /><br/>
<input class="input__bom" id="daughterInput_4" type="text" placeholder="value" inputid="4" value="20" /><br/>
<input class="input__bom" id="daughterInput_5" type="text" placeholder="value" inputid="5" value="25" /><br/>

If I understand correctly, when the input is not a number, you want to do as if the input was 3.
Some issues in your code:
$("input.input__bom").attr("inputid") is always going to evaluate to 1, as only the first matching element is used. And it is strange to use this attribute value to then retrieve that element again via its id property.
You would need a loop somewhere so to visit each of the "input__bom" elements.
== 'Nan is never going to be true. You should in fact test the main input itself to see if it represents a valid number. For that you can use isNaN.
It is a bad idea to give these elements a unique id attribute. You can use jQuery to visit them each and deal with them. There is no need for such id attribute.
Don't use the keyup event for this, as input can be given in other ways than pressing keys (e.g. dragging text with mouse, or using the context menu to paste). Use the input event instead.
There is no good reason to use event delegation here on $(document). Just bind your listener directly the main input element.
Declare your variables with var (or let, const). It is bad practice to no do that (it makes your variables global).
It seems like the 5 "bom" input elements are not really intended for input, but for output. In that case the placeholder attribute makes no sense, and they should better be marked with the readonly attribute.
$("#mainInput").on('input', function() {
var mainInput = $(this).val();
var multiplier = +mainInput; // convert to number with unary +
// default value in case input is not a valid number, or is empty
if (Number.isNaN(multiplier) || !mainInput) {
multiplier = 3;
}
$('.input__bom').each(function() {
$(this).val( multiplier * $(this).data('value') );
});
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<input id="mainInput" type="text" placeholder="Number" />
<br><br>
<input class="input__bom" type="text" readonly data-value="5" value="5"><br/>
<input class="input__bom" type="text" readonly data-value="10" value="10"><br/>
<input class="input__bom" type="text" readonly data-value="15" value="15"><br/>
<input class="input__bom" type="text" readonly data-value="20" value="20"><br/>
<input class="input__bom" type="text" readonly data-value="25" value="25" /><br/>

You have to store the default value in the data attr so then it will not multiple by result value and it will multiple by your default value. for dynamic multiplication, you can use jquery each. check below code.
$(document).on('input', 'input#mainInput', function() {
thisParentQtyValueBox = parseInt( $(this).val() );
if( Number.isNaN( thisParentQtyValueBox ) ){
thisParentQtyValueBox = 3;
}
$('.input__bom').each(function(){
$(this).val( thisParentQtyValueBox * $(this).data('value') );
});
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<input id="mainInput" type="text" placeholder="Number" />
<br><br>
<input class="input__bom" id="daughterInput_1" type="text" placeholder="value" inputid="1" data-value ="5" value="5" /><br/>
<input class="input__bom" id="daughterInput_2" type="text" placeholder="value" inputid="2" data-value ="10" value="10" /><br/>
<input class="input__bom" id="daughterInput_3" type="text" placeholder="value" inputid="3" data-value ="15" value="15" /><br/>
<input class="input__bom" id="daughterInput_4" type="text" placeholder="value" inputid="4" data-value ="20" value="20" /><br/>
<input class="input__bom" id="daughterInput_5" type="text" placeholder="value" inputid="5" data-value ="25" value="25" /><br/>

Iterate through N number of input boxes, updating each to their max value

Is there a way to give a bunch of inputs the same ID, and then iterate over them, when a checkbox is checked, and update their respective values to the MAX attribute? For example, with the following HTML:
CHECK ALL: <input type="checkbox" id="someIDname">
<input type="number" max="80" id="anotherIDname">
<input type="number" max="90" id="anotherIDname">
<input type="number" max="99" id="anotherIDname">
<input type="number" max="65" id="unrelated">
<input type="number" max="75" id="unrelated">
... and the JS is like this:
<script type="text/javascript">
$(document).ready(function() {
$('#someIDname').click(function(event) {
if(this.checked) {
$('#anotherIDname').each( function() {
var maxValue = $("#anotherIDname").attr("max");
document.getElementById("anotherIDname").value = maxValue;
});
}
});
});
</script>
I'd like to, when the checkbox is checked, have it fill in all of the MAX attributes from anything with the "anotherIDname" ID. (I'd then have three boxes, onewith 80, one with 90, one with 99. The other two are different IDs, so it would leave those alone.)
Total beginner with JS / jQuery here... The above script works on the 1st box, but does not update the others with the "anotherIDname" ID. (I thought maybe that ".each" would make it do them all, one at a time, but ... I guess that's not how it works. (I'm more of a PHP guy, normally, and that would be how something like this could maybe work if it was server-side.) Any thoughts appreciated.

There are few things wrong
id is always unique in the page.Same class is assigned to elements having same features
You should use $(this).val() to set the value
$(document).ready(function() {
$('#someIDname').click(function(event) {
if(this.checked) {
$('.anotherIDname').each( function() {
var maxValue = $(this).attr("max");
console.log(maxValue);
$(this).val(maxValue)
});
}
});
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<input type="checkbox" id="someIDname">
<input type="number" max="80" class="anotherIDname">
<input type="number" max="90" class="anotherIDname">
<input type="number" max="99" class="anotherIDname">
<input type="number" max="65" class="unrelated">
<input type="number" max="75" class="unrelated">

Added a class name and used querySelectorAll. Does this work as you want?
$(document).ready(function() {
$('#someIDname').click(function(event) {
if(this.checked) {
document.querySelectorAll('.max').forEach(a => {
a.value = a.max;
});
}
});
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
CHECK ALL: <input type="checkbox" id="someIDname">
<input type="number" max="80" id="anotherIDname" class="max">
<input type="number" max="90" id="anotherIDname" class="max">
<input type="number" max="99" id="anotherIDname" class="max">
<input type="number" max="65" id="unrelated" class="max">
<input type="number" max="75" id="unrelated" class="max">

The id must be unique in the page. So, you can't use same id in several places. However, you can use same class in several places.
So, you'll need to change the id to class for eg.:
<input type="number" max="80" class="maxinput" />
And to set the value from max attribute:
$('.maxinput').val(function() {
return $(this).attr('max')
});
However, I would suggest to use data-* instead of simple attribute:
<input type="number" data-max="80" class="maxinput" />
And get the data value:
$('.maxinput').val(function() {
return $(this).data('max')
});
But I am still in surprise why you aren't simply setting their values initially?
<input type="number" class="maxinput" value="80" />

Calculate Arrays with input field instead of span or div

I'm trying to do a simple calculation onblur with arrays but it's not firing. If I change it to a span or div it works fine. Why isn't it working with an input field?
I need it to be an input field because it's easier to store the values in a database.
<input type="text" class="input-small" name="partnumber[]">
<input type="text" class="input-small" name="partdescription[]" >
<input type="text" class="input-small" name="partprice[]" onblur="doCalc(); calculate(); ">
<input type="text" class="input-small" name="partquantity[]" onblur="doCalc(); calculate(); ">
<input type="text" readonly class="input-small parttotal" name="parttotal[]" >
Calculation
function doCalc() {
var total = 0;
$('tr').each(function() {
$(this).find('.parttotal').html($('input:eq(2)', this).val() * $('input:eq(3)', this).val());
});
$('.parttotal').each(function() {
total += parseInt($(this).text(),10);
});
}

Firstly, I wouldn't use inline events.. Here I've used delegated events, an advantage here if you dynamically add any more lines, it will still work..
Next make sure each line has some sort of wrapper for each line, here I've used a simple DIV. Yousr might be your TR..
The rest then becomes easy, as can be seen here, this example I've just included the price, qty & total, and done 2 lines for testing..
function calc() {
var h = $(this).closest('div');
var qty = h.find('[name="partquantity[]"]');
var price = h.find('[name="partprice[]"]');
var total = h.find('[name="parttotal[]"]');
total.val(qty.val() * price.val());
}
$('body').on('blur', '[name="partprice[]"],[name="partquantity[]"]', calc);
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div>
<input type="text" class="input-small" name="partprice[]">
<input type="text" class="input-small" name="partquantity[]">
<input type="text" readonly class="input-small parttotal" name="parttotal[]" >
</div>
<div>
<input type="text" class="input-small" name="partprice[]">
<input type="text" class="input-small" name="partquantity[]">
<input type="text" readonly class="input-small parttotal" name="parttotal[]" >
</div>

you can't use .html() to set the value of a textbox.
Change this line:
$(this).find('.parttotal').html($('input:eq(2)', this).val() * $('input:eq(3)', this).val());
to
$(this).find('.parttotal').val($('input:eq(2)', this).val() * $('input:eq(3)', this).val());
Note the change ('.parttotal').html becomes ('.parttotal').val

Give two text boxes the same value one is filled in using Javascript or jQuery

I have 2 textboxes with a type="number".
1 textbox is my 'master' textbox, then I have another subsequent textbox that I would like that IF the 'master' textbox is filled in with a number, the subsequent textbox would get the same value.
I thought about using the data- attribute but I am not sure how to target if the 'master' textbox is filled then, then subsequently put the same value in the sub textbox(es) with the same data- attribute.
In my example below I also use spans to create plus and minus buttons that adjust the value based on the value. This is in the JS section.
My current HTML is as follow:
<div id="masterTextboxes">
<span class="minusBtn AddMinusButton">-</span>
<input type="number" value="" placeholder="0" data-attendees="Adult" />
<span class="addBtn AddMinusButton">+</span>
<span class="minusBtn AddMinusButton">-</span>
<input type="number" value="" placeholder="0" data-attendees="Child" />
<span class="addBtn AddMinusButton">+</span>
</div>
<!--Values from Master Textboxes should populate into these textboxes as well.-->
<div id="subTextboxes">
<span class="minusBtn AddMinusButton">-</span>
<input type="number" value="" placeholder="0" data-attendees="Adult" />
<span class="addBtn AddMinusButton">+</span>
<span class="minusBtn AddMinusButton">-</span>
<input type="number" value="" placeholder="0" data-attendees="Child" />
<span class="addBtn AddMinusButton">+</span>
</div>
Javascript
<script>
$(document).ready(function () {
/*Add an minus buttons for variants*/
$(".AddMinusButton").on('click touchstart', function (event) {
event.preventDefault();
//Add button active style for touch.
var $button = $(this);
var oldValue = $button.parent().find("input").val();
var newVal = oldValue;
//Hide .decButton for oldValue
if (newVal == 0 || oldValue == 0 ) {
oldValue = 0;
}
else { $button.parent().find(".minusBtn").show(); }
if ($button.text() == "+") {
newVal = parseFloat(oldValue) + 1;
// Don't allow decrementing below zero
if (oldValue >= 1) {
newVal = parseFloat(oldValue) - 1;
}
}
$button.parent().find("input.attendeeQuantityInput").val(newVal);
//Sub textboxes should take value of master textboxes. Is this correct syntax?
//This is probably wrong.
$('#subTextboxes input').data("attendee").val(newVal);
});//End button click
});
</script>
I hope this makes sense on what I am trying to get out of this.
Thanks in advance.

I would like that IF the 'master' textbox is filled in with a number,
the subsequent textbox would get the same value.
You can do it like this:
<p>
<label>Master 1: <input type="number" id="master1" placeholder="0" /></label><br>
<label>Dependant 1: <input type="number" class="dependant1" placeholder="0" /></label>
</p>
<p>
<label>Master 2: <input type="number" id="master2" placeholder="0" /></label><br>
<label>Dependant 2: <input type="number" class="dependant2" placeholder="0" /></label><br>
<label>Dependant 2: <input type="number" class="dependant2" placeholder="0" /></label>
</p>
And in the JS:
$("input[id^='master']").on("change", function(){
var no = this.id.replace("master", "");
var selector = ".dependant" + no
$(selector).val(this.value);
});
This makes use of jQuery's attribute starts with selector and will work for any number of inputs provided the class names match.
Demo

You could do this:
HTML:
<div id="masterTextboxes">
<p>Master</p>
<input type="number" value="" placeholder="0" data-attendees="Adult" />
<input type="number" value="" placeholder="0" data-attendees="Child" />
</div>
<div id="subTextboxes">
<p>Sub</p>
<input type="number" value="" placeholder="0" data-attendees="Adult" />
<input type="number" value="" placeholder="0" data-attendees="Child" />
</div>
JS:
// On change in master inputs...
$("#masterTextboxes input", this).on("change", function() {
// Store Master inputs in master variable and Sub inputs in sub variable.
var master = $("#masterTextboxes input"),
sub = $("#subTextboxes input");
// Match master and sub values by using the master array key as reference.
$(sub[$.inArray($(this)[0], master)]).val( $(this).val() );
});
The jQuery code relies on the condition that the Sub inputs follow the same order as the Master's inside each respective div.
JSFiddle:
Here's a working JSFiddle for reference.

Jquery help create input field based on another

I am trying to create an input field when the Add input is clicked.
The input created with Jquery should be the same as the closest input field but just with info added to the name.
When the Add input is clicked the text should change to "Remove input" and if it is clicked the created input field should be removed.
My HTML:
<div class="input string optional">
<label for="company_count" class="string optional"> count</label>
<input type="text" size="50" name="company[count]" maxlength="255" id="company_count" class="string optional">
<p class="addinput">Add input</p>
</div>
<div class="input string optional">
<label for="company_navn" class="string optional"> Navn</label>
<input type="text" size="50" name="company[navn]" maxlength="255" id="company_navn" class="string optional">
<p class="addinput">Add input</p>
</div>
My Jquery
$('.addinput').toggle(function() {
}
});
Update:
The input field:
<div class="input numeric integer optional"><label for="company_prisar" class="integer optional"> Pris 1. år</label><input type="number" step="1" size="50" name="company[prisar]" id="company_prisar" class="numeric integer optional"></div>
When the add input is clicked this input is added:
<input type="number" step="1" size="50" name="company[prisarinfo]" id="company_prisarinfo" class="numeric integer optional">

If I understand your question correct then something like this should solve the problem:
$('button.add', '#companyinfo').live('click', function(e) {
var element = $(this).parents('.input').find('input').last().clone().prop('value','');
var counter = $(this).parents('.input').find('input').length + 1;
var newname = element.prop('id') + '_' + counter;
element.prop('name', newname);
element.insertAfter($(this).parents('.input').find('input').last());
$('button.remove').removeProp('disabled');
})
$('button.remove', '#companyinfo').live('click', function(e) {
$(this).parents('.input').find('input').last().remove('input');
if ($(this).parents('.input').find('input').length == 1) {
$(this).parents('.input').find('button.remove').prop('disabled', 'disabled');
}
});
Note that I've modified you html a bit, you can see a working live demo at jsFiddle.

I think you have a typo, it should read:
$('p.addinput').toggle(function(){});
Could you expand upon what you want the function to do? It's not clear to me.