Adding low to high and High to low

Toolrbar.php file

<?php
namespace JJCustomproductshowPluginCatalogBlockProductProductList;


class Toolbar extends MagentoCatalogBlockProductProductListToolbar
{


    /**
     * Set collection to pager
     *
     * @param MagentoFrameworkDataCollection $collection
     * @return MagentoCatalogBlockProductProductListToolbar
     */
public function afterGetAvailableOrders(Toolbar $subject, $availableOrders)
{
    // Remove 'position' from available orders if it exists
    if (isset($availableOrders['position'])) {
        unset($availableOrders['position']);
    }


    return $availableOrders;
}
public function setCollection($collection)
    {
        $this->_collection = $collection;


        $this->_collection->setCurPage($this->getCurrentPage());


        // we need to set pagination only if passed value integer and more that 0
        $limit = (int)$this->getLimit();
        if ($limit) {
            $this->_collection->setPageSize($limit);
        }
        if ($this->getCurrentOrder()) {
            if (($this->getCurrentOrder()) == 'position') {
                $this->_collection->addAttributeToSort(
                    $this->getCurrentOrder(),
                    $this->getCurrentDirection()
                );
            } else {
               if ($this->getCurrentOrder() == 'high_to_low') {
                   $this->_collection->setOrder('price', 'desc');
                }elseif ($this->getCurrentOrder() == 'low_to_high') {
                   $this->_collection->setOrder('price', 'asc');
               }
            }
        }
        return $this;
    }


}

di.xml

<?xml version="1.0" encoding="UTF-8"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="MagentoCustomerControllerAccountLoginPost">
        <plugin name="loginPost" type="JJCustomproductshowPluginAccountLoginPost" sortOrder="10" disabled="true"/>
    </type>
    <preference for="MagentoWishlistControllerIndexAdd" type="JJCustomproductshowControllerIndexAdd">
    </preference>
    <preference for="MagentoCatalogBlockProductProductListToolbar" type="JJCustomproductshowPluginCatalogBlockProductProductListToolbar" />
    <type name="MagentoCatalogModelConfig">
        <plugin name="custom_catalog_model_config" type="JJCustomproductshowPluginCatalogModelConfig"/>
    </type>
</config>