note

/* --------------------------------------
    *       12. Love It Button
    *  -------------------------------------- */
    $('.thm-love-btn').on('click', function(e) {
        e.preventDefault();
        var that = $(this);
        var campaign_id = that.data('campaign');
        var user_id = that.data('user');

       if( user_id != 0 && campaign_id ){
            $.ajax({
                type:"POST",
                url: ajax_objects.ajaxurl,
                data: {'action': 'thm_campaign_action', 'campaign_id': campaign_id},
                success:function(data){
                    data = JSON.parse(data);
                    if (data.success == 1){
                        that.find('.amount').html(data.number);
                        if( data.message == 'love' ){
                            that.addClass( 'active' ).parents('.themeum-campaign-post').find('.themeum-campaign-img').addClass('active');
                        }else{
                            that.removeClass( 'active' ).parents('.themeum-campaign-post').find('.themeum-campaign-img').removeClass('active');
                        }
                    }
                }
            });
        }else{
            $('#myModal').modal('show');
        }
    });



========================================

<a href="#" class="thm-love-btn <?php echo esc_attr($active); ?>" data-campaign="<?php echo get_the_ID(); ?>" data-user="<?php echo get_current_user_id(); ?>">
                        <i class="fa fa-heart-o"></i>
                    </a>

====================================





 <!-- <i class="back-heart"></i>  -->
    <span class="thm-Price-amount text-center">
        <span class="thm-love-btn"  data-campaign="<?php echo get_the_ID(); ?>" data-user="<?php echo get_current_user_id(); ?>">
            <i class="back-heart"></i>
            <span class="woocommerce-Price-amount amount latest-price">
                <?php
                    $love_count = get_post_meta( get_the_ID(),'loved_campaign_ids', true );
                    if( $love_count ){
                        echo esc_attr($love_count);
                    }else{
                        echo '0';
                    }
                 ?>
            </span>
            <span class="thm-raise-sp"><?php _e('Love it', 'backnow') ?></span>
        </span>
    </span>


=========================================

function.php

/* -------------------------------------------
 *   Love it Action
 * ------------------------------------------- */
add_action( 'wp_ajax_thm_campaign_action','themeum_campaign_action' );
add_action( 'wp_ajax_nopriv_thm_campaign_action', 'themeum_campaign_action' );
function themeum_campaign_action(){
    if ( ! is_user_logged_in()){
        die(json_encode(array('success'=> 0, 'message' => __('Please Sign In first', 'backnow') )));
    }

    $loved_campaign_ids  = array();
    $user_id             = get_current_user_id();
    $campaign_id         = sanitize_text_field($_POST['campaign_id']);
	$prev_campaign_ids   = get_user_meta($user_id, 'loved_campaign_ids', true);
	$postid 			 = get_post_meta( $campaign_id, 'loved_campaign_ids', true );

    if ($prev_campaign_ids){
        $loved_campaign_ids = json_decode( $prev_campaign_ids, true );
	}

    if (in_array($campaign_id, $loved_campaign_ids)){
        if(($key = array_search($campaign_id, $loved_campaign_ids)) !== false) {
            unset( $loved_campaign_ids[$key] );
        }
        $json_update_campaign_ids = json_encode($loved_campaign_ids);
		update_user_meta($user_id, 'loved_campaign_ids', $json_update_campaign_ids);
		if( $postid ){
			$postid = (int)$postid - 1;
			update_post_meta( $campaign_id, 'loved_campaign_ids', $postid );
		}else{
			$postid = 0;
			update_post_meta( $campaign_id, 'loved_campaign_ids', 0 );
		}
		die(json_encode(array('success'=> 1, 'number' => $postid, 'message' => 'delete' )));
    }else{
        $loved_campaign_ids[] = $campaign_id;
		update_user_meta($user_id, 'loved_campaign_ids', json_encode($loved_campaign_ids) );
		if( $postid ){
			$postid = (int)$postid + 1;
			update_post_meta( $campaign_id, 'loved_campaign_ids', $postid );
		}else{
			$postid = 1;
			update_post_meta( $campaign_id, 'loved_campaign_ids', 1 );
		}
        die(json_encode(array('success'=> 1, 'number' => $postid , 'message' => 'love' )));
    }
}