EnqueueScripts.php

<?php
namespace VendorName\PluginName;
use WordPress_ToolKit\ScriptObject;

class EnqueueScripts extends Plugin {

  function __construct() {

    // Enqueue frontend/backend scripts
    add_action( 'wp_enqueue_scripts', array( $this, 'enqueue_frontend_scripts' ) );
    add_action( 'admin_enqueue_scripts', array( $this, 'enqueue_admin_scripts' ) );

    // Inject plugin settings into page head
    $this->inject_javascript_settings();

    // Example - Load Font Awesome from CDN, if enabled in Settings Page
    $enqueue_font_awesome = $this->get_carbon_plugin_option( 'enqueue_font_awesome' );
    if( $enqueue_font_awesome ) {
      if( in_array( 'frontend', $enqueue_font_awesome) )
        add_action( 'wp_enqueue_scripts', array( $this, 'enqueue_font_awesome' ) );
      if( in_array( 'backend', $enqueue_font_awesome) )
        add_action( 'admin_enqueue_scripts', array( $this, 'enqueue_font_awesome' ) );
    }

  }

  /**
    * Enqueue scripts used on frontend of site
    * @since 0.1.0
    */
  public function enqueue_frontend_scripts() {

    // Enqueue script dependencies
    $this->enqueue_common_scripts();

    // Enqueuing custom CSS for child theme (Twentysixteen was used for testing)
    wp_enqueue_style( 'wordpress-base-plugin', Helpers::get_script_url( 'assets/css/wordpress-base-plugin.css' ), null, Helpers::get_script_version( 'assets/css/wordpress-base-plugin.css' ) );

    // Enqueue frontend JavaScript
    wp_enqueue_script( 'wordpress-base-plugin', Helpers::get_script_url( 'assets/js/wordpress-base-plugin.js' ), array( 'jquery', 'jquery-waituntilexists' ), Helpers::get_script_version( 'assets/js/wordpress-base-plugin.js' ), true );
    wp_localize_script( 'wordpress-base-plugin', $this->prefix( 'ajax_filter_params' ), array( 'ajax_url' => admin_url( 'admin-ajax.php' ) ) );

  }

  /**
    * Enqueue scripts used in WP admin interface
    * @since 0.1.0
    */
  public function enqueue_admin_scripts() {

    // Enqueue script dependencies
    $this->enqueue_common_scripts();

    // Enqueuing custom CSS for child theme (Twentysixteen was used for testing)
    wp_enqueue_style( 'wordpress-base-plugin', Helpers::get_script_url( 'assets/css/wordpress-base-plugin-admin.css' ), null, Helpers::get_script_version( 'assets/css/wordpress-base-plugin-admin.css' ) );

    // Enqueue WP Admin JavaScript
    wp_enqueue_script( 'wordpress-base-plugin-admin', Helpers::get_script_url( 'assets/js/wordpress-base-plugin-admin.js' ), array('jquery', 'jquery-waituntilexists'), Helpers::get_script_version( 'assets/js/wordpress-base-plugin-admin.js' ), true );
    wp_localize_script( 'wordpress-base-plugin-admin', $this->prefix( 'ajax_filter_params' ), array( 'ajax_url' => admin_url( 'admin-ajax.php' ) ) );

  }

  /**
    * Enqueue scripts common to the public site and WP Admin
    * @since 0.3.0
    */
  private function enqueue_common_scripts() {

    // Enqueue common (frontend/backend) JavaScript
    wp_enqueue_script( 'jquery-waituntilexists', Helpers::get_script_url( 'assets/components/jq.waituntilexists/jquery.waitUntilExists.min.js', false ), array( 'jquery' ), '0.1.0' );

  }

  /**
    * Enqueue Font Awesome
    * @since 0.1.0
    */
  public function enqueue_font_awesome() {

    wp_enqueue_style( 'font-awesome', 'https://use.fontawesome.com/releases/v5.6.1/css/all.css', null, null );
    wp_enqueue_style( 'font-awesome-shims', 'https://use.fontawesome.com/releases/v5.6.1/css/v4-shims.css', [ 'font-awesome' ], null );

  }

  /**
    * Inject JavaScript settings into header. You can add any variables/settings
    *    that you want to make available to your JavaScripts.
    * @since 0.3.0
    */
  private function inject_javascript_settings() {

    $args = array(
      'variable_name' => $this->prefix( 'plugin_settings', '_' ),
      'target' => [ 'wp', 'admin' ]
    );

    $values = array(
      'admin_bar_add_clear_cache' => $this->get_carbon_plugin_option( 'admin_bar_add_clear_cache' ),
      'admin_bar_add_clear_cache_success' => __( 'WordPress cache has been cleared.', self::$textdomain ),
      'show_clear_cache_link' => current_user_can( 'manage_options' ),
    );

    $js = new \WordPress_ToolKit\ScriptObject( $values );
    $js->injectJS( $args );

  }

}