js实现点赞功能

<button id="likeButton">点赞</button>
<span id="likeCount">0</span>

document.addEventListener('DOMContentLoaded', function() {
    const likeButton = document.getElementById('likeButton');
    const likeCount = document.getElementById('likeCount');
    let isLiked = false; // 标记当前用户是否已经点赞

    likeButton.addEventListener('click', function() {
        if (isLiked) {
            // 如果已经点赞，则取消点赞
            unlike();
        } else {
            // 如果未点赞，则点赞
            like();
        }
    });

    function like() {
        fetch('/api/like', {
            method: 'POST',
            headers: {
                'Content-Type': 'application/json'
            },
            body: JSON.stringify({ action: 'like' })
        })
        .then(response => response.json())
        .then(data => {
            if (data.success) {
                likeCount.textContent = data.likeCount;
                isLiked = true;
                likeButton.textContent = '取消点赞';
            } else {
                alert('点赞失败，请重试');
            }
        })
        .catch(error => {
            console.error('Error:', error);
            alert('点赞失败，请重试');
        });
    }

    function unlike() {
        fetch('/api/like', {
            method: 'POST',
            headers: {
                'Content-Type': 'application/json'
            },
            body: JSON.stringify({ action: 'unlike' })
        })
        .then(response => response.json())
        .then(data => {
            if (data.success) {
                likeCount.textContent = data.likeCount;
                isLiked = false;
                likeButton.textContent = '点赞';
            } else {
                alert('取消点赞失败，请重试');
            }
        })
        .catch(error => {
            console.error('Error:', error);
            alert('取消点赞失败，请重试');
        });
    }
});

const express = require('express');
const app = express();
app.use(express.json());

let likeCount = 0;

app.post('/api/like', (req, res) => {
    const action = req.body.action;
    if (action === 'like') {
        likeCount++;
    } else if (action === 'unlike') {
        likeCount--;
    } else {
        return res.status(400).json({ success: false, message: 'Invalid action' });
    }
    res.json({ success: true, likeCount: likeCount });
});

app.listen(3000, () => {
    console.log('Server is running on port 3000');
});