steps 步进函数 | 开创者教程

实例代码

<!DOCTYPE html>
<html>
<head>
    <style>
        body {
            font-family: Arial, sans-serif;
            margin: 0 auto;
            padding: 20px;
            line-height: 1.6;
        }
        h1 {
            color: #2c3e50;
            text-align: center;
            font-size: 1.5em;
            margin-bottom: 20px;
        }
        .example {
            margin-bottom: 30px;
            background: #f8f9fa;
            padding: 15px;
            border-radius: 8px;
            box-shadow: 0 2px 5px rgba(0,0,0,0.1);
        }
        .title {
            font-weight: bold;
            margin-bottom: 10px;
            padding: 5px;
            background: #e9ecef;
            border-radius: 4px;
            text-align: center;
        }
        .modern {
            color: #e74c3c;
            font-size: 1.1em;
        }
        .legacy {
            color: #7f8c8d;
            font-size: 0.9em;
            display: block;
        }
        .track {
            height: 30px;
            background: #ecf0f1;
            position: relative;
            margin: 15px 0;
            border-radius: 15px;
            overflow: hidden;
        }
        .runner {
            position: absolute;
            left: 0;
            top: 0;
            width: 30px;
            height: 30px;
            background: #3498db;
            border-radius: 50%;
            animation: run 3s infinite;
        }
        .description {
            font-size: 0.9em;
            color: #34495e;
        }
        .description strong {
            color: #2c3e50;
        }
        
        @keyframes run {
            to {
                left: calc(100% - 30px);
            }
        }
        
        .step-indicator {
            position: absolute;
            bottom: -20px;
            font-size: 12px;
            color: #3498db;
            font-weight: bold;
            transform: translateX(-50%);
        }
    </style>
</head>
<body>
    <h1>CSS steps() 函数差异演示</h1>
    <p style="text-align: center; color: #7f8c8d; margin-bottom: 20px;">观察小球在每个阶段开始/结束时的跳跃时机</p>
    
    
    <div class="example">
        <div class="title">
            <span class="modern">steps(5, jump-start)</span>
            <span class="legacy">等效于 steps(5, start)</span>
        </div>
        <div class="track">
            <div class="runner" style="animation-timing-function: steps(5, jump-start);"></div>
        </div>
        <div class="description">
            <p><strong>特点：</strong>在每步<strong>开始时</strong>立即跳跃</p>
            <p><strong>表现：</strong>第1帧就跳到20%位置，看起来像是"左对齐"</p>
        </div>
    </div>
    
    
    <div class="example">
        <div class="title">
            <span class="modern">steps(5, jump-end)</span>
            <span class="legacy">等效于 steps(5, end)</span>
        </div>
        <div class="track">
            <div class="runner" style="animation-timing-function: steps(5, jump-end);"></div>
        </div>
        <div class="description">
            <p><strong>特点：</strong>在每步<strong>结束时</strong>才跳跃</p>
            <p><strong>表现：</strong>最后一步会停在终点，看起来像是"右对齐"</p>
        </div>
    </div>
    
    
    <div class="example">
        <div class="title">
            <span class="modern">steps(5, jump-none)</span>
        </div>
        <div class="track">
            <div class="runner" style="animation-timing-function: steps(5, jump-none);"></div>
        </div>
        <div class="description">
            <p><strong>特点：</strong>在每步<strong>之间</strong>跳跃</p>
            <p><strong>表现：</strong>没有开始或结束时的停顿，最平滑的阶梯效果</p>
        </div>
    </div>
    
    
    <div class="example">
        <div class="title">
            <span class="modern">steps(5, jump-both)</span>
        </div>
        <div class="track">
            <div class="runner" style="animation-timing-function: steps(5, jump-both);"></div>
        </div>
        <div class="description">
            <p><strong>特点：</strong>在每步<strong>开始和结束</strong>都跳跃</p>
            <p><strong>表现：</strong>相当于多一个中间步骤，最明显的阶梯效果</p>
        </div>
    </div>
    
    <script>
        // 添加步数指示器
        document.addEventListener('DOMContentLoaded', function() {
            const runners = document.querySelectorAll('.runner');
            runners.forEach(runner => {
                const indicator = document.createElement('div');
                indicator.className = 'step-indicator';
                runner.parentNode.appendChild(indicator);
                
                function updateIndicator() {
                    const rect = runner.getBoundingClientRect();
                    const trackRect = runner.parentNode.getBoundingClientRect();
                    const percent = (rect.left - trackRect.left) / (trackRect.width - rect.width) * 100;
                    const step = Math.min(5, Math.max(1, Math.ceil(percent / 20)));
                    indicator.textContent = `步骤 ${step}`;
                    indicator.style.left = `${percent}%`;
                }
                
                updateIndicator();
                
                let lastTime = 0;
                function trackAnimation(time) {
                    if (time - lastTime > 100) {
                        updateIndicator();
                        lastTime = time;
                    }
                    requestAnimationFrame(trackAnimation);
                }
                requestAnimationFrame(trackAnimation);
            });
        });
    </script>
</body>
</html>