JSFiddle - React, Tailwind, and code Playground

HTML

<table id="matable">
	<tr>
    	<td><b>Nom du site</b></td>
        <td><b>Adresse</b></td>
        <td><b>Adresse Suite</b></td>
        <td><b>CP</b></td>
        <td><b>Ville</b></td>
        <td><b>Pays</b></td>
        <td><b>Nom du contact</b></td>
        <td><b>t&eacute;l</b></td>
        <td><b>Fax</b></td>
        <td><b>Mobile</b></td>
        <td><b>E-Mail</b></td>
    </tr>
    <tr>
    	<td><input type="text" id="nomad" name="nomad" /></td>
        <td><input type="text" id="ad1" name="ad1" /></td>
        <td><input type="text" id="ad2" name="ad2" /></td>
        <td><input type="text" id="cp" name="cp" /></td>
        <td><input type="text" id="ville" name="ville" /></td>
        <td><input type="text" id="pays" name="pays" /></td>
        <td><input type="text" id="nomco" name="nomco" /></td>
        <td><input type="text" id="tel" name="tel" /></td>
        <td><input type="text" id="fax" name="fax" /></td>
        <td><input type="text" id="mobile" name="mobile" /></td>
        <td><input type="text" id="email" name="email" /></td>
    </tr>
</table>
<button id="add_line">ajouter une ligne</button>

JavaScript

$("#add_line").click(function(){
    
   var line = $("#matable tr:eq(1)").clone();
   var nb_line = $("#matable tr").length;
    
    $(line).find( "td input" ).each(function( index ) { 
       var input = $(line).find( "td input" )[index];
       var id = $(input).attr("id");
       $($(line).find( "td input" )[index]).attr('id', id + nb_line);
    });
    
    $("#matable").append(line);

});