document.addEventListener('DOMContentLoaded', function() { const main = document.getElementById('main'); let adBox = null; let scale = null; // 初始化广告容器（自动创建，不需要HTML） function initAdBox() { adBox = document.createElement('div'); adBox.className = 'right-bottom-ad-wrap'; adBox.innerHTML = ` `; document.body.appendChild(adBox); } // 初始化标尺 function initScale() { scale = document.createElement('div'); scale.className = 'leica-scale'; scale.innerHTML = ` 0.70.811.21.5 23510∞m `; document.body.appendChild(scale); } // 滚动监听 function check() { const bottom = main.getBoundingClientRect().bottom; if (bottom < 0) { if (!adBox) initAdBox(); if (!scale) initScale(); adBox.classList.add('show'); scale.classList.add('show'); } else { if (adBox) adBox.classList.remove('show'); if (scale) scale.classList.remove('show'); } } window.addEventListener('scroll', check); check(); }