无插件点赞功能由 #Fatesinger# 提供，不过 @大发 好像删除了该篇文章。

实现原理大体是通过自定义字段保存赞数量，通过Cookie记录并禁止重复赞。

具体的代码如下：

function.php

/**
 * AJAX点赞
 * by: #fatesinger.com
 * modify: #biji.io #bgbk.org
 */
function dotGood()
{
    global $wpdb, $post;
    $id = $_POST["um_id"];
    if ($_POST["um_action"] == 'topTop') {
        $specs_raters = get_post_meta($id, 'dotGood', true);
        $expire = time() + 99999999;
        $domain = ($_SERVER['HTTP_HOST'] != 'localhost') ? $_SERVER['HTTP_HOST'] : false; // make cookies work with localhost
        setcookie('dotGood_' . $id, $id, $expire, '/', $domain, false);
        if (!$specs_raters || !is_numeric($specs_raters)) update_post_meta($id, 'dotGood', 1);
        else update_post_meta($id, 'dotGood', ($specs_raters + 1));
        echo get_post_meta($id, 'dotGood', true);
    }
    die;
}
add_action('wp_ajax_nopriv_dotGood', 'dotGood');
add_action('wp_ajax_dotGood', 'dotGood');

JavaScript

$.fn.postLike = function () {
    if ($(this).hasClass('done')) {
        alert('点多了伤身体~');
        return false;
    } else {
        $(this).addClass('done');
        var id = $(this).data("id"),
            action = $(this).data('action'),
            rateHolder = $(this).children('.count');
        var ajax_data = {
            action: "dotGood",
            um_id: id,
            um_action: action
        };
        $.post("/wp-admin/admin-ajax.php", ajax_data,
            function (data) {
                $(rateHolder).html(data);
            });
        return false;
    }
};
$(".dotGood").click(function () {
    $(this).postLike();
});

CSS

.post-like{margin:10% 0 0;position:relative;}
.post-like a.dotGood{height:30px;line-height:30px;width:30px;font-size:24px;text-align:center;display:inline-block;cursor: pointer;position:relative;}
.post-like a.dotGood.done{color: #e2264d;}
.post-like a.dotGood span{position:absolute;display:inline-block;top:0;left:26px;width:auto;font-size:14px;}
.post-like a.dotGood span:before{content:'+';}

HTML

<a href="javascript:;" data-action="topTop" data-id="<?php the_ID(); ?>"
   class="dotGood <?php echo isset($_COOKIE['dotGood_' . $post->ID]) ? 'done' : ''; ?>">
    &hearts;
    <span class="count"><?php echo ($dot_good=get_post_meta($post->ID, 'dotGood', true)) ? $dot_good : '0'; ?></span>
</a>

至此，点赞功能就可以实现了。