why is my form being submitted twice when pressing enter or when using a barcode scanner?

Question

I have tried everything and it seems that the form is submitted twice only when pressing enter or using a barcode scanner which I want to use. I does not happen when clicking the "submit button". At first I thought I was executing the query twice but it's not the case. This is my code:

HTML file

<form id="formulario_ingreso" class="form-horizontal" onsubmit="return ingresar();" method="POST">
<div class="row">
    <div class="col-sm-6">
        <div class="form-group">
            <div class="controls">
                <input id="codigo" type="number" name="codigo" class="form-control" placeholder="Código" autofocus>
            </div>
        </div>
    </div>
    <div class="col-sm-6">
            <div class="form-group">
                <select class="select2 form-control" id="nombre" name="nombre">
                <option value="">Nombre (Solo si no existe código)</option>
                <?php
                    while ($row = mysqli_fetch_assoc($perfiles_query)){
                        echo '<option value="'.$row["id"].'">'.$row["nombres"].' '.$row["apellidos"].'</option>';
                    }
                ?>
            </select>
        </div>
    </div>
</div>
<button type="button" class="btn btn-primary" onclick="ingresar()">Ingresar</button>
</form>

SCRIPT file

<script>
   $("#formulario_ingreso").submit(function(e) {
      e.preventDefault();
   });
</script>
<script>
   function ingresar(){
       var codigo = $("#codigo").val();
       var nombre = $("#nombre").val();
       if(codigo){

           $.post("evento/ingresar_asistencia.php", { codigo: codigo },
           function(data) {
                 $('#results').html(data);
                 $('#formulario_ingreso')[0].reset();
           });



       }else if(nombre){
           $.post("evento/ingresar_asistencia.php", { nombre: nombre },
           function(data) {
                 $('#results').html(data);
                 $('#formulario_ingreso')[0].reset();
           });
       }
    };

</script>

PHP FILE

<?php
require_once '../../../config.php';

if(isset($_POST["codigo"])){
    $codigo = $_POST["codigo"];
    echo $codigo;

    $asistencia_query = mysqli_query($link, "INSERT INTO asistencia (id_perfil, id_evento) VALUES (2,1) ");

}

Answer 1

I have tried your code but in my case, it's a one-time call ingresar() function when I click on the button.

Please remove onsubmit="return ingresar();" from you form tag. I think this one is creating the issue