Trying to prepend a Hashtag symbol to the_tags links [closed]

Using JS is not really the best possible solution as it can be disabled on client side. You can also use PHP like regular expressions and DOM to alter the links, but I really think the most reliable way to achive this is to rebuild the list throught the term_link-post_tag filter which is located inside the get_the_term_list() function which is used by get_the_tag_list which in turn is used by the_tags().

The following is untested, but you can try something like this

add_filter( 'term_link-post_tag', function ( $links )
{
    // Return if $links are empty
    if ( empty( $links ) )
        return $links;

    // Reset $links to an empty array
    unset ( $links );
    $links = [];

    // Get the current post ID
    $id = get_the_ID();
    // Get all the tags attached to the post
    $taxonomy = 'post_tag';
    $terms = get_the_terms( $id, $taxonomy );

    // Make double sure we have tags
    if ( !$terms )
        return $links; 

    // Loop through the tags and build the links
    foreach ( $terms as $term ) {
        $link = get_term_link( $term, $taxonomy );

        // Here we add our hastag, so we get #Tag Name with link
        $links[] = '<a href="' . esc_url( $link ) . '" rel="tag">#' . $term->name . '</a>';
    }

    return $links;
});