How to easily add/remove cells from a Table (Shifting existent cells) - css

Question

I want a table to automatically align cells to be two per row, meaning that if a add/remove a cell, cells will shift to be two per row (with one on last row if total number of cells is odd).
Example:
<table>
<tr>
<td>old1</td> <td>old2</td>
</tr>
<tr>
<td>old3</td> <td>old4</td>
</tr>
</table>
To this:
<table>
<tr>
<td>NEW</td> <td>old1</td>
</tr>
<tr>
<td>old2</td> <td>old3</td>
</tr>
<tr>
<td>old4</td>
</tr>
</table>
Notice the automatically added row.

Answer 1

I'll show you three ways to accomplish what you need,
css3 Using flex (modern browsers only)
css Using inline-table (problem with cell height but usable as sort-of fallback)
jquery Using standard <table> (All browsers!)
Using CSS3's FLEX
.table{
display: flex;
flex-wrap: wrap;
}
.cell{
width:50%;
background:#ddd;
}
<div class="table">
<div class="cell">NEW</div>
<div class="cell">OLD1</div>
<div class="cell">OLD2</div>
<div class="cell">OLD3<br>new line</div>
<div class="cell">OLD4</div>
</div>
Using inline-table (issue with cell height)
display: table;   for the parent element and
display: inline-table for the inner DIVs:
.table{
display:table;
}
.cell{
display:inline-table;
width:50%; /* With percentage you simulate "how-many-per-Row" */
background:#ddd;
}
<div class="table">
<div class="cell">NEW</div>
<div class="cell">OLD1</div>
<div class="cell">OLD2</div> <!-- Works but notice this cell height -->
<div class="cell">OLD3<br>new line</div>
<div class="cell">OLD4</div>
</div>
You could use the inline-table as a fallback for older browsers - it's not the exact same result but without JavaScript it's the best you could get.
Take a look in the specs about the display property: https://developer.mozilla.org/en-US/docs/Web/CSS/display
Using <table>, <tr> and <td> and JavaScript (jQuery)
If you want to stick to good 'ol table elements you can use "a bit" of jQuery.
In that case it's a bit more complicated (see code-comments):
jQuery(function($){ // DOM is now ready
var $table = $("table"); // Get your table
var maxRowCells = 2; // only 2-per-Row
var counter = 0; // just a dummy counter
function prependNewCell(){
var $newCell = $("<td/>", {html: "NEW"+(++counter)});
// Is the last row full?
if($table.find("tr:last td").length == maxRowCells){
// If true, append a new TR to TABLE to shift TD's to
$table.append( $("<tr/>") );
}
// Shift all last TD's to the next row:
$table.find("tr:not(:last)").each(function(){
var $tdLast = $(this).find("td").last();
$(this).next("tr").prepend( $tdLast );
});
// Finally. Prepend the new TD element to the first TR
$table.find("tr").first().prepend( $newCell );
}
$("button").on("click", prependNewCell);
});
td{
width:50%;
background:#ddd;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<button>ADD NEW CELL ON TOP</button>
<table>
<tr>
<td>OLD1</td>
<td>OLD2</td>
</tr>
<tr>
<td>OLD3</td>
<td>OLD4</td>
</tr>
</table>

Answer 2

table {
empty-cells: hide;
}