纯js实现网页返回顶部功能(万能的兼容目前所有浏览器)
在web2.0时代，越来越多的网站如雨后春笋般的冒了出来。而且这些网站提供了很多我们常见的功能。如：返回顶部等等小特性。
那么这些功能是如何实现的呢。这里将为大家提供一些快速使用的万能代码。
(function() {
var btnId = '__gotop';
var isIE = !!window.ActiveXObject && /msie (\d)/i.test(navigator.userAgent) ? RegExp['$1'] : false;
function $() {
return document.getElementById(arguments[0]);
}
function getScrollTop() {
return ('pageYOffset' in window) ? window.pageYOffset
: document.compatMode === "BackCompat"
&& document.body.scrollTop
|| document.documentElement.scrollTop ;
}
function bindEvent(event, func) {
if (window.addEventListener) {
window.addEventListener(event, func, false);
} else if (window.attachEvent) {
window.attachEvent('on' + event, func);
}
}
bindEvent('load',
function() {
var css = 'background-color:#999;width:50px;height:50px;position:fixed;right:100px;bottom:30px;border-radius:10px;cursor:pointer;display:none;';
if (isIE && isIE < 7) {
css += '_position:absolute;_top:expression(eval(document.documentElement.scrollTop+document.documentElement.clientHeight-30-this.offsetHeight-(parseInt(this.currentStyle.marginTop,10)||0)-(parseInt(this.currentStyle.marginBottom,10)||0)))';
var style = document.createStyleSheet();
style.cssText = '*html{background-image:url(about:blank);background-attachment:fixed;}';
}
var html = '<div style="height: 0;width: 0;border:14px solid #999999;border-top: 0 none;border-bottom:14px solid #fff;position: relative;margin:12px 0 0 11px;"><div style="width:8px;height:7px;position:absolute;top:14px;left:-4px;background-color:#fff;overflow: hidden;"></div></div>';
var el = document.createElement('DIV');
el.id = btnId;
el.style.cssText = css;
el.innerHTML = html;
document.body.appendChild(el);
el.onclick = function() {
(function() {
var top = getScrollTop();
if (top > 0) {
window.scrollTo(0, top / 1.2)
setTimeout(arguments.callee, 10);
}
})();
};
el.onmouseover = function() {
$(btnId).firstChild.style.borderBottom = '14px solid #ddd';
$(btnId).firstChild.firstChild.style.backgroundColor = '#ddd';
};
el.onmouseout = function() {
$(btnId).firstChild.style.borderBottom = '14px solid #fff';
$(btnId).firstChild.firstChild.style.backgroundColor = '#fff';
};
}
);
bindEvent('scroll',
function() {
var top = getScrollTop(), display = 'none';
if (top > 0) {
display = 'block';
}
if ($(btnId)) $(btnId).style.display = display;
});
})();在看看测试页面吧。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>返回顶部按钮</title> <meta name="keywords" content=""/> <meta name="Description" content=""/> <script type="text/javascript" src="abc.js"></script> </head> <body style="height:2000px;"> </body> </html>看看效果吧：
