HTML, CSS, JS 实现弹窗 Loading 效果

<div id='loading'>
    <div class='spinner'></div>
</div>
<style>
#loading {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    z-index: 9999;
    display: none;
}

.spinner {
    border: 4px solid rgba(255, 255, 255, 0.3);
    border-top: 4px solid #fff;
    border-radius: 50%;
    width: 40px;
    height: 40px;
    margin: auto;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    0% {
        transform: rotate(0deg);
    }
    100% {
        transform: rotate(360deg);
    }
}
</style>
<script>
function showLoading() {
    document.getElementById('loading').style.display = 'block';
}

function hideLoading() {
    document.getElementById('loading').style.display = 'none';
}
</script>
<p>调用 showLoading() 函数显示 Loading 弹窗，调用 hideLoading() 函数隐藏 Loading 弹窗。</p>