Develop Reference

Why does my function return undefined, especially the .split()parts?

So in essence I get the value of input, then try to divide into into different tags via the comma with this
var noteTags = document.getElementsByClassName("noteTag").value;
Tag = noteTags.split(",");
But in console, the split(",") is undefined
Edit: Sorry I forgot to mention that the noteTag element is input, does this change how the code works in any way?

There are two issues,
getElementsByClassName returns an array-like collection of elements (a NodeList).
And instead of value it should be innerText.
Try like below
var noteTags = document.getElementsByClassName("noteTag")[0].innerText;
Tag = noteTags.split(",");

You are using the split() method on an array. You are also trying to access the value property, whereby you should probably use innerText.

You can use querySelector then you dont need using a key[0] to select the element.
const noteTags = document.querySelector("#noteTag");
console.log(noteTags)
Tag = noteTags.innerHTML.split(",");
console.log(Tag)
<div id="noteTag">en,jp,fr</div>

jQuery: easier way to use .clone() than described below?

If you execute in the console on this page
var cloned = $(".question").clone(true);
$(".question").addClass("first");
var clonedStr = cloned[0].outerHTML || new XMLSerializer().serializeToString(cloned[0]);
$(".question").after(clonedStr);
you will clone the question (there will be two questions on the page, but the first one will be with the .first class). That's what is needed.
Is there any simpler way to do this with jQuery? I'm confused of the third string in the code above and believe it could be simpler. Any ideas?
Thank you.

If you don't use the HTML as string, then don't get it. Just use the jQuery object:
var cloned = $(".question").clone(true);
$(".question").addClass("first").after(cloned);
Also, you can do it one line:
$(".question").after($(".question").clone(true)).first().addClass("first");

You could use insertAfter to insert the cloned element after changing the class. You don't need to convert the element in the jQuery object to a string, you can use that object within the function itself:
var $question = $('.question');
var $cloned = $question.clone(true).insertAfter($question);
$question.addClass('first');

jQuery throws an error that element.find() is not a function

I have written a small JS to iterate through a set of matched elements and perform some task on each of them.
Here is the code:
var eachProduct = $(".item");
eachProduct.each(function(index, element){
var eachProductContent = element.find(".product-meta").clone();
});
When I console log element it outputs properly and the exact objects. Why should jquery throw this error?

because element is a dom element not a jQuery object
var eachProductContent = $(element).find(".product-meta").clone();
Inside the each() handler you will get the dom element reference as the second parameter, not a jQuery object reference. So if you want to access any jQuery methods on the element then you need to get the elements jQuery wrapper object.

You are calling .find() on a plain JS object, But that function belongs to Jquery object
var eachProductContent = $(element).find(".product-meta").clone();
You can convert it to a jquery object by wrapping it inside $(). And in order to avoid this kind of discrepancies you can simply use $(this) reference instead of using other.

Use $(this) for current Element
var eachProductContent = $(this).find(".product-meta").clone();

you should change "element" to "this":
var eachProduct = $(".item");
eachProduct.each(function(index, element){
var eachProductContent = $(this).find(".product-meta").clone();
});

same classes multiple times how to get object using index

I want to get an element's value based on the class and the index that it was created.
Fiddle here:
Code (not working)
alert($('.demo-default').length); //works
//alert ( $('.demo-default').get(2).val());
x = $('.demo-default').get(2);
alert(x).val();
//alert ( $('.demo-default').index(2 ).val()); //NW
WORKING :
http://jsfiddle.net/A324T/7/

You need to use eq() instead of x to invoke val() on it, or use .value
With
x = $('.demo-default').get(2); //x is DOM element.
Use
x.value; //Prop on DOM element
With
x = $('.demo-default').eq(2); //x is Jq object.
Use
x.val(); //method on jq object

get() returns the DOM element.
You want to use eq()

First, you use alert function wrong.
Also, jQuery.get() method will return a DOM element. val() method works only with jQuery objects. To fetch the value, simply use value property.
alert(x.value);

HTMLInputElement has no method 'val'

I'm looping through cells in a table row. each cell has a text box in it, and I want to take the value of the text box and push it onto an array.
function dothing() {
var tds = $('#'+selected+' td');
var submitvals = new Array();
tds.each(function(i) {
var val = $(this).children('input')[0].val();
submitvals.push(val);
});
}
Theres more to the function, but this is all that is relevant. For some reason, when I run this code, I get "HTMLInputElement has no method 'val'." I thought that input elements were supposed to have a val() method in jQuery that got the value so this makes no sense. Am I missing something, or doing it wrong?

val() is a jQuery method. .value is the DOM Element's property. Use [0].value or .eq(0).val()....

.val() is a jQuery function, not a javascript function. Therefore, change:
var val = $(this).children('input')[0].val()
To:
var val = $(this).children('input:eq(0)').val()

function dothing() {
var tds = $('#'+selected+' td');
var submitvals = new Array();
tds.each(function(i) {
var val = $($(this).children('input')[0]).val();
submitvals.push(val);
});
}

.val() is a jquery method. Using [0] returns the DOM element, not the jquery element
var val = $(this).children('input:first').val();

What I don't understand, is why none of the suggested syntaxes on this or other questions similar to this seem to work for me. I had to do trial and error and eventually had to use:
MySelectElement.value = x;
It also didn't help that the Visual Studio Intellisense suggestions offer a whole other range of unworking method names, such as ValueOf().