TinyMCE button for custom shortcode

gistfile1.php

<?php

// [myCustomShortcode type="tip"]Dette er et godt tips[/myCustomShortcode]
function clientName_myCustomShortcode_func( $atts, $content = null ) {
    $args = shortcode_atts( array(
        'type' => 'tip',
    ), $atts );
    if ( ! $content ) {
        return '';
    }
    if ( $args[ 'type' ] === 'foo' ) {
        $headline = 'Foo';
    } else {
        $headline = 'Bar';
    }
    return '<span class="tip type-' . $args[ 'type' ] . '"><span class="tipHeadline">' . $headline . '</span><span class="tipText">' . strip_tags( trim( $content ), '<br/>' ) . '</span></span>';
}
add_shortcode( 'myCustomShortcode', 'clientName_myCustomShortcode_func' );

function clientName_add_myCustomShortcode_button() {

    // Check user permissions
    if ( ! current_user_can( 'edit_posts' ) && ! current_user_can( 'edit_pages' ) ) {
        return;
    }

    // Verify the post type
    global $typenow;
    if( ! in_array( $typenow, array( 'post', 'page' ) ) )
        return;

    // Check if WYSIWYG is enabled
    if ( get_user_option( 'rich_editing' ) == 'true') {
        add_filter( 'mce_external_plugins', 'clientName_myCustomShortcode_btn_add_tinymce_plugin' );
        add_filter( 'mce_buttons', 'clientName_myCustomShortcode_btn_register_tinymce_plugin' );
    }
}
add_action( 'admin_head', 'clientName_add_myCustomShortcode_button' );

function clientName_myCustomShortcode_btn_add_tinymce_plugin($plugin_array) {
    $plugin_array[ 'clientName_myCustomShortcode_button' ] = get_template_directory_uri() .'/assets/admin/scripts/clientName_myCustomShortcode_btn.js';
    return $plugin_array;
}

function clientName_myCustomShortcode_btn_register_tinymce_plugin( $buttons ) {
   array_push( $buttons, 'clientName_myCustomShortcode_button' );
   return $buttons;
}

function clientName_shortcode_btns_css() {
    wp_enqueue_style( 'clientNamemyCustomShortcode', get_template_directory_uri() .'/assets/admin/styles/clientName_shortcode_btns.css' );
}
add_action( 'admin_enqueue_scripts', 'clientName_shortcode_btns_css' );