原生JavaScript是怎样实现渐隐效果的
function id(name) { return document.getElementById(name); } //遍历函数 function each(arr, callback) { if (arr.forEach) { arr.forEach(callback); } else { for (var i = 0, len = arr.length; i < len; i++) callback.call(this, arr[i], i, arr); } } function fadeIn(elem) { setOpacity(elem, 0) for (var i = 0; i < 20; i++) { (function() { var pos = i * 5; setTimeout(function() { setOpacity(elem, pos) }, i * 25); })(i); } } function fadeOut(elem) { for (var i = 0; i <= 20; i++) { (function() { var pos = 100 - i * 5; setTimeout(function() { setOpacity(elem, pos) }, i * 25); })(i); } } // 设置透明度 function setOpacity(elem, level) { if (elem.filters) { elem.style.filter = "alpha(opacity=" + level + ")"; } else { elem.style.opacity = level / 100; } }