opensourcepos/app/Views/items/form_inventory.php

<?php
/**
 * @var object $item_info
 * @var array $stock_locations
 * @var array $item_quantities
 * @var string $controller_name
 */
?>

<div id="required_fields_message"><?= lang('Common.fields_required_message') ?></div>
<ul id="error_message_box" class="error_message_box"></ul>

<?= form_open("items/saveInventory/$item_info->item_id", ['id' => 'item_form', 'class' => 'form-horizontal']) ?>
    <fieldset id="inv_item_basic_info">

        <div class="form-group form-group-sm">
            <?= form_label(lang('Items.item_number'), 'name', ['class' => 'control-label col-xs-3']) ?>
            <div class="col-xs-8">
                <div class="input-group">
                    <span class="input-group-addon input-sm"><span class="glyphicon glyphicon-barcode"></span></span>
                    <?= form_input([
                        'name'     => 'item_number',
                        'id'       => 'item_number',
                        'class'    => 'form-control input-sm',
                        'disabled' => '',
                        'value'    => $item_info->item_number
                    ]) ?>
                </div>
            </div>
        </div>

        <div class="form-group form-group-sm">
            <?= form_label(lang('Items.name'), 'name', ['class' => 'control-label col-xs-3']) ?>
            <div class="col-xs-8">
                <?= form_input([
                    'name'     => 'name',
                    'id'       => 'name',
                    'class'    => 'form-control input-sm',
                    'disabled' => '',
                    'value'    => $item_info->name
                ]) ?>
            </div>
        </div>

        <div class="form-group form-group-sm">
            <?= form_label(lang('Items.category'), 'category', ['class' => 'control-label col-xs-3']) ?>
            <div class="col-xs-8">
                <div class="input-group">
                    <span class="input-group-addon input-sm"><span class="glyphicon glyphicon-tag"></span></span>
                    <?= form_input([
                        'name'     => 'category',
                        'id'       => 'category',
                        'class'    => 'form-control input-sm',
                        'disabled' => '',
                        'value'    => $item_info->category
                    ]) ?>
                </div>
            </div>
        </div>

        <div class="form-group form-group-sm">
            <?= form_label(lang('Items.stock_location'), 'stock_location', ['class' => 'control-label col-xs-3']) ?>
            <div class="col-xs-8">
                <?= form_dropdown('stock_location', $stock_locations, current($stock_locations), ['onchange' => 'fill_quantity(this.value)', 'class' => 'form-control']) ?>
            </div>
        </div>

        <div class="form-group form-group-sm">
            <?= form_label(lang('Items.current_quantity'), 'quantity', ['class' => 'control-label col-xs-3']) ?>
            <div class="col-xs-4">
                <?= form_input([
                    'name'     => 'quantity',
                    'id'       => 'quantity',
                    'class'    => 'form-control input-sm',
                    'disabled' => '',
                    'value'    => to_quantity_decimals(current($item_quantities))
                ]) ?>
            </div>
        </div>

        <div class="form-group form-group-sm">
            <?= form_label(lang('Items.add_minus'), 'quantity', ['class' => 'control-label col-xs-3 text-danger required']) ?>
            <div class="col-xs-4">
                <?= form_input([
                    'name'  => 'newquantity',
                    'id'    => 'newquantity',
                    'class' => 'form-control input-sm'
                ]) ?>
            </div>
        </div>

        <div class="form-group form-group-sm">
            <?= form_label(lang('Items.inventory_comments'), 'description', ['class' => 'control-label col-xs-3']) ?>
            <div class="col-xs-8">
                <?= form_textarea([
                    'name'  => 'trans_comment',
                    'id'    => 'trans_comment',
                    'class' => 'form-control input-sm'
                ]) ?>
            </div>
        </div>

    </fieldset>
<?= form_close() ?>

<script type="text/javascript">
    // Validation and submit handling
    $(document).ready(function() {
        $('#item_form').validate($.extend({
            submitHandler: function(form) {
                $(form).ajaxSubmit({
                    success: function(response) {
                        dialog_support.hide();
                        table_support.handle_submit("<?= esc($controller_name) ?>", response);
                    },
                    dataType: 'json'
                });
            },

            errorLabelContainer: '#error_message_box',

            rules: {
                newquantity: {
                    required: true,
                    number: true
                }
            },

            messages: {
                newquantity: {
                    required: "<?= lang('Items.quantity_required') ?>",
                    number: "<?= lang('Items.quantity_number') ?>"
                }
            }
        }, form_support.error));
    });

    function fill_quantity(val) {
        const item_quantities = <?= json_encode(esc($item_quantities, 'raw')) ?>;
        document.getElementById('quantity').value = parseFloat(item_quantities[val]).toFixed(<?= quantity_decimals() ?>);
    }
</script>