Controlling dropdown menus filled with AJAX responseData

When it comes to Javascript, JQuery has always been a reliable companion for me. However, there are instances where I encounter challenges that require some extra effort to overcome. Today happens to be one of those days. I've stumbled upon an issue that is proving to be quite complex for me to resolve. Let me elaborate below.

The Scenario

<select name="one" id="one">
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
    ....
</select>

<select name="two" id="two">
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
    ....
</select>

<select name="three" id="three">
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
    ....
</select>

Challenges Faced

I have managed to achieve the cascading dropdown functionality using JQuery successfully. The problem arises when the third dropdown triggers a refresh. After the refresh, all select values get reset, causing another unwanted refresh cycle.

What I aim to accomplish is to ensure that the first refresh sets all select values without triggering subsequent refreshes on selection in the third dropdown.

If further clarification is needed, please feel free to ask. Any advice or support would be greatly appreciated.

Status Update

if (false !== rootpfgroup && false !== hoofdpfgroup && false !== subpfgroup) {
    $('#one').val(rootpfgroup).trigger('change');
    $('#two').val(hoofdpfgroup).trigger('change');
    $('#three').val(subpfgroup);
}

My current approach only sets the first dropdown value and triggers ajax calls for subsequent dropdown options based on selections. Can someone shed light on how to improve this process? Your input is highly valued. Thank you in advance.

Answer №1

My suggestion is to set the selected dropdown value using PHP instead of relying on JavaScript, which would solve your refresh issue and ensure that the selected value persists without needing JS:

<?php
    $one = '';
    $two = '';
    $three = '';

    if (!empty($_POST['one'])) {
        $one = $_POST['one'];
    }
    if (!empty($_POST['two'])) {
        $two = $_POST['two'];
    }
    if (!empty($_POST['three'])) {
        $three = $_POST['three'];
    }
?>

$(document).on('change', '#three', function() {
    var form = $('#form');
    var item = $(this).val();
    var url = basePath + 'item/' + item;
    form.attr('action', url);
    form.submit();
});

<form action="" method="POST" id="form">
    <select name="one" id="one">
        <option value="1" <?php if ($one == 1):?>selected<?php endif;?>>One</option>
        <option value="2" <?php if ($one == 2):?>selected<?php endif;?>>Two</option>
        <option value="3" <?php if ($one == 3):?>selected<?php endif;?>>Three</option>
    </select>
    <select name="two" id="two">
        <option value="1" <?php if ($two == 1):?>selected<?php endif;?>>One</option>
        <option value="2" <?php if ($two == 2):?>selected<?php endif;?>>Two</option>
        <option value="3" <?php if ($two == 3):?>selected<?php endif;?>>Three</option>
    </select>
    <select name="three" id="three">
        <option value="1" <?php if ($three == 1):?>selected<?php endif;?>>One</option>
        <option value="2" <?php if ($three == 2):?>selected<?php endif;?>>Two</option>
        <option value="3" <?php if ($three == 3):?>selected<?php endif;?>>Three</option>
    </select>
</form>

To avoid repetition in your PHP code, you could consider implementing loops based on your data structure.

Answer №2

<?php
$red = '';
$blue = '';
$green = '';

if (!empty($_POST['red'])) {
    $red = $_POST['red'];
}
if (!empty($_POST['blue'])) {
    $blue = $_POST['blue'];
}
if (!empty($_POST['green'])) {
    $green = $_POST['green'];
}
?>

$(document).ready(function() {
    var red = '<?= $red; ?>';
    var blue = '<?= $blue; ?>';
    var green = '<?= $green; ?>';

    if (red != '') {
        $('#red').val(red);
    }
    if (blue != '') {
        $('#blue').val(blue);
    }
    if (green != '') {
        $('#green').val(green);
    }
});

$(document).on('change', '#green', function() {
    var form = $('#color-form');
    var color = $(this).val();
    var link = baseURL + 'color/' + color;
    form.attr('action', link);
    form.submit();
});

<form action="" method="POST" id="color-form">
    <select name="red" id="red">
        <option value="1">Red</option>
        <option value="2">Blue</option>
        <option value="3">Green</option>
    </select>
    <select name="blue" id="blue">
        <option value="1">Red</option>
        <option value="2">Blue</option>
        <option value="3">Green</option>
    </select>
    <select name="green" id="green">
        <option value="1">Red</option>
        <option value="2">Blue</option>
        <option value="3">Green</option>
    </select>
</form>

These adjustments ensure that the values are correctly assigned.

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