使用jquery为输入添加焦点

Question

为什么这段代码行不通？ 如果我将焦点设置行替换为测试警报，则可以。

$('#rendeles_termek').on('change', function() {
    $('#rendeles_mennyiseg').focus();
});

<select  name="rendeles_termek" class="form-control chosen-select" id="rendeles_termek">

<input class="form-control" id="rendeles_mennyiseg" name="rendeles_mennyiseg" type="text" value="<?php echo isset($_POST["rendeles_mennyiseg"])?$_POST["rendeles_mennyiseg"]:""; ?>"/>

更新：这行得通。 如果我把它从onchange拿出来，只能放入文档准备好。

$(document).ready(function(e) { $('#rendeles_mennyiseg').focus();
                    $('#rendeles_termek').on('change', function() {
                         //$('#rendeles_mennyiseg').focus();
                         //alert("xxx");
                      });
                });

更新2：

<select  name="rendeles_termek" class="form-control chosen-select" id="rendeles_termek">
                    <?php
                    $ertek = isset($_POST["rendeles_termek"]) ? $_POST["rendeles_termek"] : '' ;
                    $get_gyartok = mysqli_query($kapcs, "SELECT termek_id, termek_nev, termek_egyseg FROM termek WHERE termek_status = 1 
                    ORDER BY termek_nev ASC");
                    if(mysqli_num_rows($get_gyartok) > 0 )
                    {
                        while($gy = mysqli_fetch_assoc($get_gyartok))
                        {
                            $selected = $ertek == $gy['termek_id'] ? ' selected="selected"':'';
                            echo '<option ' . $selected . ' value="' . $gy['termek_id'] . '">' . $gy['termek_nev'] . ' - ('.$egysegek[$gy['termek_egyseg']].')</option>';
                        }
                    } 
                    ?>
                    </select>

<input class="form-control" id="rendeles_mennyiseg" name="rendeles_mennyiseg" type="text" value="<?php echo isset($_POST["rendeles_mennyiseg"])?$_POST["rendeles_mennyiseg"]:""; ?>"/>

Answer 1

 $('#rendeles_termek').on('change', function() { $('#rendeles_mennyiseg').focus(); }); 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script> <select name="rendeles_termek" class="form-control chosen-select" id="rendeles_termek"> <option>Option1 </option> <option>Option2 </option> </select> <input class="form-control" id="rendeles_mennyiseg" name="rendeles_mennyiseg" type="text" placeholder="Focus Me" /> 

我希望这能够帮到你。

Answer 2

我用下面的代码解决了这个问题：

$(document).ready(function(e) {

                      $('#rendeles_termek').on("change", function() {
                           setTimeout(function(ev) { 
                                $('#rendeles_mennyiseg').focus(); }, 
                           1);
                      });


                });