Wordpress walker class for wp_nav_menu() - change item and submenu class also add caret icon inside has-childiren item.

functions.php

<?php

class My_Walker_Nav_Menu extends Walker_Nav_Menu {

  
  function start_lvl(&$output, $depth = 0, $args = array()) {
    $indent = str_repeat("\t", $depth);
    $output .= "\n$indent<ul class=\"dropdown-menu\">\n";
  }

  function start_el(&$output, $item, $depth = 0, $args = array(), $id = 0)
    {

      global $wp_query;
    $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';

    $class_names = $value = '';

    $classes = empty( $item->classes ) ? array() : (array) $item->classes;
    $classes[] = 'menu-item-' . $item->ID;

    $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );

    // Check our custom has_children property.here is the points
    if(in_array('menu-item-has-children', $classes ) && $depth == 0) {
       // Your Code
      $class_names = ' class="dropdown custom-drop ' . esc_attr( $class_names ) . '"';
    } else {
      $class_names = ' class="' . esc_attr( $class_names ) . '"';
    }

    

    $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );
    $id = strlen( $id ) ? ' id="' . esc_attr( $id ) . '"' : '';

    $output .= $indent . '<li' . $id . $value . $class_names .'>';

    $attributes  = ! empty( $item->attr_title ) ? ' title="'  . esc_attr( $item->attr_title ) .'"' : '';
    $attributes .= ! empty( $item->target )     ? ' target="' . esc_attr( $item->target     ) .'"' : '';
    $attributes .= ! empty( $item->xfn )        ? ' rel="'    . esc_attr( $item->xfn        ) .'"' : '';
    $attributes .= ! empty( $item->url )        ? ' href="'   . esc_attr( $item->url        ) .'"' : '';

    $item_output = $args->before;

    // Check our custom has_children property.here is the points
    if(in_array('menu-item-has-children', $classes ) && $depth == 0) {
    $item_output .= '<i class="caret hidden-xs"></i>';
    }
    $item_output .= '<a'. $attributes .'>';
    $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;
    $item_output .= '</a>';
    $item_output .= $args->after;

    $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );

        
    }
}