Javascript 我有一个三层分类系统，你首先需要选择最上面的分类，然后是中间的，然后是底部的。中间类别的选项取决于顶部，底部类别的选项取决于中间类别。所以它有点像一个三层依赖系统。。。 <div id="selection"> <?php

我有一个三层分类系统，你首先需要选择最上面的分类，然后是中间的，然后是底部的。中间类别的选项取决于顶部，底部类别的选项取决于中间类别。所以它有点像一个三层依赖系统。。。

<div id="selection">
    <?php
        // Top level part selection
        echo "<select name='firstLevelParts' id='select1'>";
        foreach ($category_primary as $category_item):
            echo "<option value = '".$category_item['cat_primary_id']."'>".$category_item['cat_primary_name']."</option>";
        endforeach;
        echo "</select>";


        // Second level part selection (This should be updated, based on selection in top level menu)
        echo "<select name='secondLevelParts' id='select2'>";
        foreach ($category_secondary as $cat_sec_item):
             echo "<option value='".$cat_sec_item['cat_secondary_code']."'>".$cat_sec_item['cat_secondary_name']."</option>"; 
        endforeach;
        echo "</select>";
    ?>

</div>


<script>
    $("#select1").change(function() { 
        if(typeof $(this).data('options') === "undefined")){
            /*Taking an array of all options-2 and kind of embedding it on the select1*/
            $(this).data('options',$('#select2 option').clone());
            } 
        var id = $(this).val();
        var options = $(this).data('options').filter('[value=' + id + ']');
        $('#select2').html(options);
    });
</script>

<div id="selection">
<select name='firstLevelParts' id='select1'>
 <option value = '1'>Terræn</option>
 <option value = '2'>Fundamentsystem</option>
 <option value = '3'>Vægsystem</option>
 <option value = '4'>Dæksystem</option>
 <option value = '5'>Tagsystem</option>
</select>

<select name='secondLevelParts' id='select2'>
 <option value='1'>Jordprofil</option>
 <option value='2'>Befæstet Areal</option>
 <option value='3'>Beplantning</option>
 <option value='1'>Fundamentkonstruktion</option>
 <option value='2'>Bærelag</option>
 <option value='3'>Åbning</option>
 <option value='4'>Lukning</option>
 <option value='5'>Inddækning</option>
 <option value='6'>Afslutning</option>
 <option value='7'>Afskærmning</option>
 <option value='8'>Fuge</option>
 <option value='9'>Samling</option>
 <option value='10'>Overflade</option>
</select>  
</div>

<script>
    $("#select1").change(function() { 
        if(typeof $(this).data('options') === "undefined")){
            /*Taking an array of all options-2 and kind of embedding it on the select1*/
            $(this).data('options',$('#select2 option').clone());
            } 
        var id = $(this).val();
        var options = $(this).data('options').filter('[value=' + id + ']');
        $('#select2').html(options);
    });
</script> 

<script>
    $(document).ready(function() {
        $("#select1").change(function() { 
            // your code
        });
    });
</script>