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adding a new cell to a table using javascript

I have a button which is named reject and when it is clicked it is supposed to show a form with a text and another button.
Everything is working fine except it only add a cell to the first row only, no matter where the reject button is or whether it in the second or third row it will show the new cell after the first row.
i want the small form to be added in the same row where the reject button was clicked.
this my code:
<table asp-controller="Home" asp-action="Pending" class="table table-bordered table-sm table-striped" id="myTable">
<thead>
<tr>
<th>Id</th>
<th>Email</th>
<th>Status</th>
<th>Check Time</th>
</tr>
</thead>
<tbody id="demo">
#if (Model == null)
{
<tr>
<td colspan="7" class="text-center">No Model Data</td>
</tr>
}
else
{
#foreach (var p in Model)
{
<tr>
<td>#p.Id</td>
<td>#p.Email</td>
#if (#p.CheckOut == null)
{
<td>Offline</td>
<td>#p.CheckIn</td>
}
else
{
<td>Online</td>
<td>#p.CheckOut</td>
}
<td>
<button name="button" value="accept" asp-action="Accept" asp-route-id="#p.Id" class="btn btn-success">Accept Request</button>
<button id="re" class="btn btn-danger" data-id="#p.Id" onclick="fun()">Reject Request</button>
</td>
<td style="display:none;" id="comment">
<form >
<input type="text" name="newcomment" id="newcomment" />
<button name="button" value="reject" asp-action="Reject" asp-route-id="id" class="btn btn-primary">Comment</button>
</form>
</td>
</tr>
}
}
</tbody>
</table>
<script type="text/javascript">
function fun() {
document.getElementById("comment").style.display = 'block';
}

You can use JQuery to show the td area .
Firstly , modify this line :
<button id="re" class="btn btn-danger" data-id="#p.Id" onclick="fun()">Reject Request</button>
To
<button id="re" class="btn btn-danger" data-id="#p.Id" onclick="fun(this)">Reject Request</button>
And modify your js function to find the next td of current button :
function fun(elem) {
$(elem).closest('td').next('td').show();
}

2 Tables on one page - buttons on Rows to run different script

I have a page with 2 tables and each row has a 'Select' button which needs to run a script when clicked. I've got this working with the first table but can't work out how to get it working with both tables.
Here's the HTML for the tables:
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" />
<h2>Select Main</h2>
<div>
<br />
<table class="table table-condensed table-striped table-bordered">
<thead>
<th scope="col">Code</th>
<th scope="col">Description</th>
<th class="text-center" scope="col">Select</th>
</thead>
<tbody>
<tr class="" id="SK5543333">
<td>BJ2345</td>
<td>Laptop 13 inch display</td>
<td class="text-center"><button type="button" class="btn btn-success btn-sm">Select</button></td>
</tr>
<tr class="" id="SK3241235213">
<td>AZ77656</td>
<td>Laptop 15 inch display</td>
<td class="text-center"><button type="button" class="btn btn-success btn-sm">Select</button></td>
</tr>
</tbody>
</table>
</div>
<h2>Select Accessories</h2>
<div>
<br />
<table class="table table-condensed table-striped table-bordered">
<thead>
<th scope="col">Code</th>
<th scope="col">Description</th>
<th class="text-center" scope="col">Select</th>
</thead>
<tbody>
<tr class="" id="SK3412541">
<td>MM42412341</td>
<td>Mouse</td>
<td class="text-center"><button type="button" class="btn btn-success btn-sm">Select</button></td>
</tr>
<tr class="" id="SK95390485">
<td>KB42341243</td>
<td>Keyboard</td>
<td class="text-center"><button type="button" class="btn btn-success btn-sm">Select</button></td>
</tr>
<tr class="" id="SK42353">
<td>USB421341234</td>
<td>USB Adapter</td>
<td class="text-center"><button type="button" class="btn btn-success btn-sm">Select</button></td>
</tr>
<tr class="" id="SK543647585">
<td>PWR363456534</td>
<td>POWER ADAPTER</td>
<td class="text-center"><button type="button" class="btn btn-success btn-sm">Select</button></td>
</tr>
</tbody>
</table>
</div>
I need to run a different script when users select from the top/Main table and another script when users select from the bottom/Accessories table. Here's my script that runs when the Select button from the first table is clicked:
$(document).ready(function() {
$('button.btn-success:not([type="submit"])').click(function() {
// Remove the classes from all of the TR elements
$(this).parents('table').find('tr').removeClass('success warning danger');
var productID = $(this).closest('tr').attr('id');
console.log(productID);
$this = $(this);
// add the success class to the row and remove the danger class if it was present
$this.closest('tr').addClass("success");
$this.closest('tr').removeClass("danger");
// update the hidden input with the selected productID
$('#productID').val(productID);
});
});
Not sure how to have another version of this that only runs when the Select button from the 2nd table is clicked?

Was interrupted writing the answer but you could try something like this:
const selectHelper =
($me,classToAdd,inputSelector) => {
$me.parents("table")
.eq(0)
.find("tr")
.removeClass("success warning danger");
const id =
$me.parents("tr")
.eq(0)
.addClass(classToAdd)
.attr("id")
;
$(inputSelector).val(id);
}
;
const clickActions = {
one:(e,$me)=>
selectHelper(
$me
,"warning"
,"#inputidOne"
)
,two:(e,$me)=>
selectHelper(
$me
,"success"
,"#inputidTwo"
)
};
$(document.body)
.on(
"click"
,`[data-action-click]`
,e=>{
const action = e.target.getAttribute("data-action-click");
if(typeof clickActions[action] === "function"){
clickActions[action](e,$(e.target))
}
debugger;
}
)
The button needs a data-action-click attribute that has the name of the function you want to execute when clicked:
<button
type="button"
data-action-click="two"
class="btn btn-success btn-sm"
>
Select
</button>

I believe this is what you're looking for:
$(document).ready(function() {
$("table:first").find('button[type!="submit"]').click(function() {
$("table:first").find("tr").removeClass("success warning danger");
$(this).parents("tr").addClass("success");
$("#productID").val($(this).parents("tr").attr("id"));
});
$("table").eq(1).find('button[type!="submit"]').click(function() {
$("table").eq(1).find("tr").removeClass("success warning danger");
//Do whatever color you want
$(this).parents("tr").addClass("warning");
//Wasn't provided this snippet so I just made up accessoryID
$("#accessoryID").val($(this).parents("tr").attr("id"));
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" />
<h2>Select Main</h2>
<div>
<br />
<table class="table table-condensed table-striped table-bordered">
<thead>
<tr>
<th>Code</th>
<th>Description</th>
<th class="text-center">Select</th>
</tr>
</thead>
<tbody>
<tr id="SK5543333">
<td>BJ2345</td>
<td>Laptop 13 inch display</td>
<td class="text-center"><button type="button" class="btn btn-success btn-sm">Select</button></td>
</tr>
<tr id="SK3241235213">
<td>AZ77656</td>
<td>Laptop 15 inch display</td>
<td class="text-center"><button type="button" class="btn btn-success btn-sm">Select</button></td>
</tr>
</tbody>
</table>
</div>
<h2>Select Accessories</h2>
<div>
<br />
<table class="table table-condensed table-striped table-bordered">
<thead>
<tr>
<th>Code</th>
<th>Description</th>
<th class="text-center">Select</th>
</tr>
</thead>
<tbody>
<tr id="SK3412541">
<td>MM42412341</td>
<td>Mouse</td>
<td class="text-center"><button type="button" class="btn btn-success btn-sm">Select</button></td>
</tr>
<tr id="SK95390485">
<td>KB42341243</td>
<td>Keyboard</td>
<td class="text-center"><button type="button" class="btn btn-success btn-sm">Select</button></td>
</tr>
<tr id="SK42353">
<td>USB421341234</td>
<td>USB Adapter</td>
<td class="text-center"><button type="button" class="btn btn-success btn-sm">Select</button></td>
</tr>
<tr id="SK543647585">
<td>PWR363456534</td>
<td>POWER ADAPTER</td>
<td class="text-center"><button type="button" class="btn btn-success btn-sm">Select</button></td>
</tr>
</tbody>
</table>
</div>
.eq This returns a jQuery object from a list of jQuery objects by index, whereas indexing with brackets will return HTML content.
P.S. You don't really need class="" and scope="col" in the table, the HTML I provided doesn't have those. The only real point of the class attribute is to assign multiple CSS attributes easily, unless you're using classes as selectors. Same with scope, I've made many tables and never used scope.
Also, when you do a thead, you need to add a tr before you add the headers. I fixed that in the code above. (Yes, this does mean that tables support multiple header rows).

Javascript for adding table row after user input

I am trying to create a bill calculator that requires user input of their bill type and cost (i will get on to all the calculations after).
At the minute i have got a bootstrap table which is currently 3 rows.
My question is how do i get a new row for each time the user enters their input?
I have a "Bill type field" where the user would enter the type of bill they have.
Then i have the "Amount" for the user to enter how much it will cost.
Finally i have the "Have Paid?" button where the user would click to finish the bill.
Onclick of that button, i would like a new row to be inserted.
Any help would be very much appreciated.
This is my current HTML:
<div class="container">
<h2>Bill Table</h2>
<p>Select the bill type to see how much it will cost</p>
<table class="table table-bordered table-content">
<thead>
<tr>
<th class="table-content">Bill type</th>
<th class="table-content" ">Amount (£)</th>
<th class="table-content">Is paid?</th>
</tr>
</thead>
<tbody>
<tr>
<td><input type="text" id="billType1"></td>
<td><input type="number" id="amountType1"/></td>
<td id="btnContainer1">
<button class="btn btn-sm btn-success yesBtn" id="yesPaid1">Yes</button>
<img class="greenTickImg" src="css/greentick.png">
</td>
</tr>
<tr>
<td>Mary</td>
<td><input type="number" id="Food"/></td>
<td>
<button class="btn btn-sm btn-success yesBtn">Yes</button>
<img class="greenTickImg" src="css/greentick.png">
</td>
</tr>
<tr>
<td>July</td>
<td><input type="number" id="Drink"/></td>
<td>
<button class="btn btn-sm btn-success yesBtn">Yes</button>
<img class="greenTickImg" src="css/greentick.png">
</td>
</tr>
</tbody>
</table>
Thanks!

Just to start, see following code:
<!DOCTYPE html>
<html>
<head>
<script src="https://code.jquery.com/jquery-3.1.0.js"></script>
</head>
<body>
<div class="container">
<h2>Bill Table</h2>
<p>Select the bill type to see how much it will cost</p>
<table class="table table-bordered table-content">
<thead>
<tr>
<th class="table-content">Bill type</th>
<th class="table-content">Amount (£)</th>
<th class="table-content">Is paid?</th>
</tr>
</thead>
<tbody id="myGrid">
<tr>
<td><input type="text" id="billType1"></td>
<td><input type="number" id="amountType1"/></td>
<td id="btnContainer1">
<button class="btn btn-sm btn-success yesBtn" id="yesPaid1">Yes</button>
<img class="greenTickImg" src="css/greentick.png">
</td>
</tr>
<tr>
<td>Mary</td>
<td><input type="number" id="Food"/></td>
<td>
<button class="btn btn-sm btn-success yesBtn">Yes</button>
<img class="greenTickImg" src="css/greentick.png">
</td>
</tr>
<tr>
<td>July</td>
<td><input type="number" id="Drink"/></td>
<td>
<button class="btn btn-sm btn-success yesBtn">Yes</button>
<img class="greenTickImg" src="css/greentick.png">
</td>
</tr>
</tbody>
</table>
<script>
$(".yesBtn").click(function(){
var name = $("#billType1").val();
var amount = $("#amountType1").val();
$("#myGrid").append("<tr><td>" + name + "</td><td>" + amount + "</td></tr>")
$("#billType1").val("");
$("#amountType1").val("");
});
</script>
</body>
</html>

Let assume that your button has id="havePaidButton" and your table id="billTable" and the fields have ids billType, amount and isPaid, respectively.
Your code in the jQuery should look like this:
$('#havePaidButton').off().on('click', function() {
('#billTable tr:last).after('<tr><td>' + ('#billType').val() + '</td><td>' + ('#amount').val() + '</td><td>' + $('#isPaid').val() + '</td>');
});

How to Move selected table tr's to another table?

I have got two tables mytable1 and mytable2
I am trying to move the checked tr rows (from table mytable1) to different table mytable2
I have tried as following
$(document).ready(function() {
$(document).on("click", ".movemultiple", function(event)
{
$('.mytable1 > tbody > tr').each(function() {
$(this).find('td:eq(0) .updatecheckboxvalueindb:checked')
});
});
});
.fa fa-check
{
background-color:red!importnt
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table class="mytable1 table table-bordered table-hover" id="videosfromtagstable">
<thead>
<tr class="existingvideos">
<th>Action</th>
<th>Name</th>
<th>File</th>
<th>Badge</th>
<th>Equipments</th>
</tr>
</thead>
<tbody class="connectedSortable ui-sortable">
<tr video-id="37" title="" class="newvideos exercises-add-table-content">
<td class="removecheckboxtd" style="vertical-align: middle ; display:block;"><label class="mt-checkbox mt-checkbox-outline"><input class="new-checkbox updatecheckboxvalueindb" value="new_flag" type="checkbox"><span></span></label></td>
<td>crunches</td>
<td>ht4_970_979.mp4</td>
<td>
<span class="btn btn-sm btn-success btn-circle">Push Ups</span>
</td>
<td><i class="fa fa-check"></i></td>
</tr>
<tr video-id="38" title="" class="newvideos exercises-add-table-content">
<td class="removecheckboxtd" style="vertical-align: middle ; display:block;"><label class="mt-checkbox mt-checkbox-outline"><input class="new-checkbox updatecheckboxvalueindb" value="new_flag" type="checkbox"><span></span></label></td>
<td>Sit Ups</td>
<td>ht4_970_345.mp4</td>
<td>
<span class="btn btn-sm btn-success btn-circle">Push Ups</span>
</td>
<td><i class="fa fa-check"></i></td>
</tr>
</tbody>
</table>
<br><br>
<button type="button" class="btn red default movemultiple">Move </button>
<br><br>
<table class="mytable2 table table-bordered table-hover" id="videosexistingtable">
<tbody class="connectedSortable ui-sortable">
<tr class="existingvideos">
<th>Name</th>
<th>File</th>
<th>Badge</th>
<th>Equipments</th>
<th>Action</th>
</tr>
<tr class="existingvideos" video-id="34">
<td>Push Ups</td>
<td>ht4_970_285.mp4</td>
<td>
<span class="btn btn-sm btn-success btn-circle">Push Ups</span>
</td>
<td>
<i class="fa fa-check"></i>
</td>
<td class="deletevidetd"><a data-videoid="34" class="fa fa-trash remove-delete-icon deletevideo" title="Delete"></a></td>
</tr>
</tbody>
</table>
Could you please let me know how to do this ?
http://jsfiddle.net/o2gxgz9r/1879/

You could use jQuery .closest() to get the closest table row (or table cell) and jQuery .remove() to remove the table cell with the checkbox from DOM:
$(document).ready(function () {
$(document).on('click', '.movemultiple', function() {
var $myTable2Body = $('.mytable2 tbody');
$('.mytable1 .updatecheckboxvalueindb:checked').each(function(index, item) {
var $checkbox = $(item);
$myTable2Body.append($checkbox.closest('tr'));
$checkbox.closest('td').remove();
});
});
});
.fa fa-check
{
background-color:red!importnt
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table class="mytable1 table table-bordered table-hover" id="videosfromtagstable">
<thead>
<tr class="existingvideos">
<th>Action</th>
<th>Name</th>
<th>File</th>
<th>Badge</th>
<th>Equipments</th>
</tr>
</thead>
<tbody class="connectedSortable ui-sortable">
<tr video-id="37" title="" class="newvideos exercises-add-table-content">
<td class="removecheckboxtd" style="vertical-align: middle ; display:block;"><label class="mt-checkbox mt-checkbox-outline"><input class="new-checkbox updatecheckboxvalueindb" value="new_flag" type="checkbox"><span></span></label></td>
<td>crunches</td>
<td>ht4_970_979.mp4</td>
<td>
<span class="btn btn-sm btn-success btn-circle">Push Ups</span>
</td>
<td><i class="fa fa-check"></i></td>
</tr>
<tr video-id="38" title="" class="newvideos exercises-add-table-content">
<td class="removecheckboxtd" style="vertical-align: middle ; display:block;"><label class="mt-checkbox mt-checkbox-outline"><input class="new-checkbox updatecheckboxvalueindb" value="new_flag" type="checkbox"><span></span></label></td>
<td>Sit Ups</td>
<td>ht4_970_345.mp4</td>
<td>
<span class="btn btn-sm btn-success btn-circle">Push Ups</span>
</td>
<td><i class="fa fa-check"></i></td>
</tr>
</tbody>
</table>
<br><br>
<button type="button" class="btn red default movemultiple">Move </button>
<br><br>
<table class="mytable2 table table-bordered table-hover" id="videosexistingtable">
<tbody class="connectedSortable ui-sortable">
<tr class="existingvideos">
<th>Name</th>
<th>File</th>
<th>Badge</th>
<th>Equipments</th>
<th>Action</th>
</tr>
<tr class="existingvideos" video-id="34">
<td>Push Ups</td>
<td>ht4_970_285.mp4</td>
<td>
<span class="btn btn-sm btn-success btn-circle">Push Ups</span>
</td>
<td>
<i class="fa fa-check"></i>
</td>
<td class="deletevidetd"><a data-videoid="34" class="fa fa-trash remove-delete-icon deletevideo" title="Delete"></a></td>
</tr>
</tbody>
</table>
JSFiddle

like this?
$(document).on("click", ".movemultiple", function(event){
$('.updatecheckboxvalueindb:checked').parents('tr').appendTo('.mytable2').find('.removecheckboxtd').remove();
});
check out the fiddle : http://jsfiddle.net/h9q8o340/

How get the value in <tr>

I need to get the text in <tr>. This is my html code:
<table class="table" style="" id="tabella_username_aggiunti">
<thead>
<tr>
<th>Username</th>
<th>Cancella</th>
</tr>
</thead>
<tbody id="tbody_aggiungi_utente"><tr id="aggiungiprova"><td>prova</td><td><button id="eliminaprova" type="button" class="btn btn-danger btn-sm"><i class="fa fa-times" aria-hidden="true"></i></button></td></tr></tbody>
</table>
I need to extract the first <td> in <tr> that is "prova" in this example so I use this jquery code:
$('#tbody_aggiungi_utente').children('tr').each(function(i) {
console.log("TABELLA " + JSON.stringify(i)+" Tabella "+JSON.stringify($(this)));
//array_user.push($(this).attr('id').replace('aggiungi', ''));
});
But it doesn't work because it prints me TABELLA 0 Tabella {"0":{},"context":{},"length":1}
Anyone can help me?

$('#tbody_aggiungi_utente').children('tr').each(function(i) {
console.log("TABELLA " + JSON.stringify(i)+" Tabella "+$(this).first().text());
//array_user.push($(this).attr('id').replace('aggiungi', ''));
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table class="table" style="" id="tabella_username_aggiunti">
<thead>
<tr>
<th>Username</th>
<th>Cancella</th>
</tr>
</thead>
<tbody id="tbody_aggiungi_utente">
<tr id="aggiungiprova"><td>prova</td><td><button id="eliminaprova" type="button" class="btn btn-danger btn-sm"><i class="fa fa-times" aria-hidden="true"></i></button></td></tr>
</tbody>
</table>

You should use a better selector instead of children. Then you need do select the td inside your each.
$('#tbody_aggiungi_utente tr').each(function(i) {
var firstTd = $("td:eq(0)", this);
console.log("TABELLA " + JSON.stringify(i) + " Tabella " + JSON.stringify(firstTd.text()));
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table class="table" style="" id="tabella_username_aggiunti">
<thead>
<tr>
<th>Username</th>
<th>Cancella</th>
</tr>
</thead>
<tbody id="tbody_aggiungi_utente">
<tr id="aggiungiprova">
<td>prova</td>
<td>
<button id="eliminaprova" type="button" class="btn btn-danger btn-sm"><i class="fa fa-times" aria-hidden="true"></i>
</button>
</td>
</tr>
</tbody>
</table>
Or you loop the td's directly:
$('#tbody_aggiungi_utente tr td:first-of-type').each(function(i) {
console.log("TABELLA " + JSON.stringify(i) + " Tabella " + JSON.stringify($(this).text()));
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table class="table" style="" id="tabella_username_aggiunti">
<thead>
<tr>
<th>Username</th>
<th>Cancella</th>
</tr>
</thead>
<tbody id="tbody_aggiungi_utente">
<tr id="aggiungiprova">
<td>prova</td>
<td>
<button id="eliminaprova" type="button" class="btn btn-danger btn-sm"><i class="fa fa-times" aria-hidden="true"></i>
</button>
</td>
</tr>
<tr id="aggiungiprova">
<td>prova 2</td>
<td>
<button id="eliminaprova" type="button" class="btn btn-danger btn-sm"><i class="fa fa-times" aria-hidden="true"></i>
</button>
</td>
</tr>
</tbody>
</table>

replace each(function(i) with each(function(i,v) and then console.log( $(v).text().trim());
Output will be 'prova'
$('#tbody_aggiungi_utente').children('tr').each(function(i,v) {
console.log( $(v).text().trim());
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<table class="table" style="" id="tabella_username_aggiunti">
<thead>
<tr>
<th>Username</th>
<th>Cancella</th>
</tr>
</thead>
<tbody id="tbody_aggiungi_utente">
<tr id="aggiungiprova">
<td>prova</td>
<td>
<button id="eliminaprova" type="button" class="btn btn-danger btn-sm">
<i class="fa fa-times" aria-hidden="true"></i></button>
</td>
</tr>
</tbody>
</table>

Use children.
$(this).children('td:eq(0)').html());
$('#tbody_aggiungi_utente > tr').each(function(i) {
console.log("TABELLA " + JSON.stringify(i)+
" Tabella "+JSON.stringify($(this).children('td:eq(0)').html()));
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table class="table" style="" id="tabella_username_aggiunti">
<thead>
<tr>
<th>Username</th>
<th>Cancella</th>
</tr>
</thead>
<tbody id="tbody_aggiungi_utente">
<tr id="aggiungiprova"><td>prova</td><td><button id="eliminaprova" type="button" class="btn btn-danger btn-sm"><i class="fa fa-times" aria-hidden="true"></i></button></td></tr>
<tr id="aggiungiprova1"><td>prova1</td><td><button id="eliminaprova" type="button" class="btn btn-danger btn-sm"><i class="fa fa-times" aria-hidden="true"></i></button></td></tr>
</tbody>
</table>

Take a look at CSS Selectors. jQuery can select elements using the same methods.
console.log(jQuery("#aggiungiprova td:first-child"));
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table class="table" style="" id="tabella_username_aggiunti">
<thead>
<tr>
<th>Username</th>
<th>Cancella</th>
</tr>
</thead>
<tbody id="tbody_aggiungi_utente">
<tr id="aggiungiprova">
<td>prova</td>
<td>
<button id="eliminaprova" type="button" class="btn btn-danger btn-sm"><i class="fa fa-times" aria-hidden="true"></i>
</button>
</td>
</tr>
</tbody>
</table>

This should work...
a = $('#tabella_username_aggiunti tr th')
console.log(a.text())
//or
a.each(function(a, el) {
console.log($(el).text())
})
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table class="table" style="" id="tabella_username_aggiunti">
<thead>
<tr>
<th>Username</th>
<th>Cancella</th>
</tr>
</thead>
<tbody id="tbody_aggiungi_utente">
<tr id="aggiungiprova">
<td>prova</td>
<td>
<button id="eliminaprova" type="button" class="btn btn-danger btn-sm"><i class="fa fa-times" aria-hidden="true"></i>
</button>
</td>
</tr>
</tbody>
</table>

$("#aggiungiprova td").first().text();
Gives the content of the first td in the tr named "aggiungiprova".
If you need to get all names in the entire list, then:
var names = [];
$("#tabella_username_aggiunti tr").each(function(){
names.push( $("td",this).first().text());
});
// names is now an array of all names
Or you name [sic] all name TDs with class and iterate them for easier-to-read code and faster execution:
<table>
<tr><td class="name-cell">My Name</td><td>other things</td></tr>
<tr><td class="name-cell">My Name</td><td>other things</td></tr>
</table>
JS:
$('.name-cell').each(function(){
// $(this).text()
});