143 lines
4.7 KiB
JavaScript
143 lines
4.7 KiB
JavaScript
/**
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* 页面滚动条不是在最顶端时 页面出现top按钮，点击回到最顶端,按钮隐藏
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*
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* 使用 直接引入 <script src="./js/GoTop.js" id="js_gotop"></script>
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*/
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(function() {
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//获取当前js路径 然后处理图片路径 即绝对路径 （避免在多处引用图片路径不对）
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var path = document.getElementById('js_gotop').src;
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path_out = path.replace("js/GoTop.js","images/gotop_out.png");
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path_over = path.replace("js/GoTop.js","images/gotop_over.png");
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// html 元素
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var div = document.createElement('div');
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div.id = "gotop";
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div.onmouseout = function(e){this.firstChild.src = path_out};
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div.onmouseover = function(e){this.firstChild.src = path_over};
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div.setAttribute("style","display:'';position:fixed;width:30px;height:30px;bottom:50px;right:50px;opacity:0;margin: 20px");
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document.body.appendChild(div);
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var inner = '<img border=0 src='+'"'+path_out+'"'+'>';
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document.getElementById('gotop').innerHTML = inner;
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//屏幕滚动 元素淡入淡出 参数设置
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window.onscroll = function() {
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getScrollTop() > 0 ? fadein(div,100,1000,5): fadeout(div,0,1000,5);
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};
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//元素点击事件
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div.onclick = function() {
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var goTop = setInterval(scrollMove, 10);
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function scrollMove() {
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setScrollTop(getScrollTop() / 1.1);
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if (getScrollTop() < 1) clearInterval(goTop);
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}
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};
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/**
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* 获取滚动条的高度
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*
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* @returns {number} 滚动条高度
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*/
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function getScrollTop() {
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return document.documentElement.scrollTop + document.body.scrollTop;
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}
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/**
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* 设置滚动条的值
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*
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* @param value
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*/
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function setScrollTop(value) {
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if (document.documentElement.scrollTop) {
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document.documentElement.scrollTop = value;
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} else {
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document.body.scrollTop = value;
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}
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}
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/**
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* 元素透明度设置 浏览器兼容
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*
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* @param element 元素
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* @param opacity 透明度 0·100 正整数
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*/
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function setOpacity(element,opacity){
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//兼容firfox Chrome 和新版的IE
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if(element.style.opacity !== undefined)
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{
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element.style.opacity = opacity/100;
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}
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else {
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element.style.filter = "alpha(opacity = "+ opacity +")"; //兼容老版的IE
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}
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}
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/**
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* 淡入
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*
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* @param element 元素
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* @param opacity 最终透明度 0`100 正整数
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* @param time 总共时间 单位 毫秒
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* @param value 每次变化值 0`100 正整数
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*/
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function fadein(element, opacity,time,value){
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if(element){
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//获取当前的透明度
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var v = element.style.opacity || element.style.filter.replace("alpha(opacity=","").replace(")","");
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v = v > 1 ? v*1 : v*100;
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//变化透明度
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var changeopacity = opacity - v;
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if(changeopacity <= 0) return;
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//元素可见
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element.style.display = "";
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//变化次数
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var count = changeopacity/value;
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//变化时间间隔
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var speed = time/count;
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var timer = null;
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timer = setInterval(function(){
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if(v<opacity) {
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v +=value;
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setOpacity(element,v);
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}
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else{
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clearInterval(timer);
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}
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},speed);
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}
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}
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/**
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* 淡出
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*
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* @param element 元素
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* @param opacity 最终透明度 0`100 正整数
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* @param time 总共时间 单位 毫秒
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* @param value 每次变化值 0`100 正整数
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*/
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function fadeout(element,opacity,time,value){
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if(element){
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//获取当前的透明度
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var v = element.style.filter.replace("alpha(opacity=","").replace(")","") || element.style.opacity || 100;
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v = v > 1 ? v*1 : v*100;
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//变化透明度
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var changeopacity = v - opacity;
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if(changeopacity <= 0) return;
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//变化次数
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var count = changeopacity/value;
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//变化时间间隔
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var speed = time/count;
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var timer = null;
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timer = setInterval(function(){
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if((v-value) >= opacity){
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v -= value;
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setOpacity(element,v);
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}
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else {
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clearInterval(timer);
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element.style.display = "none";
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}
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},speed)
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}
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}
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})();
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