How to get the value of Select without using submit(either post or get)

        <option value="" disabled>Sort by</option>
<?php
    $categories = get_categories(['exclude' => 1]);

    foreach ($categories as $category) {
        echo "<option>$category->name </option>";
    }
?>
        <option>Newest</option>
        <option>Oldest</option>
        <option>Title Asc</option>
        <option>Title Desc</option>

    </select>

and i want to get the value of the selected option without redirecting or using form for me to use it in function

how can i do that?