一段js代码，点击效果可以看百度首页 https://www.baidu.com/ 
(function() {
    // 1. 设置画布与透明度
    const canvas = document.createElement('canvas');
    const ctx = canvas.getContext('2d');
    canvas.style.position = 'fixed';
    canvas.style.left = '0';
    canvas.style.top = '0';
    canvas.style.width = '100%';
    canvas.style.height = '100%';
    canvas.style.zIndex = '9999';
    canvas.style.pointerEvents = 'n...