純js實現網頁返回頂部功能(萬能的相容目前所有瀏覽器)

業餘草發表於2014-09-30
JS網頁瀏覽器

純js實現網頁返回頂部功能(萬能的相容目前所有瀏覽器)

在web2.0時代，越來越多的網站如雨後春筍般的冒了出來。而且這些網站提供了很多我們常見的功能。如：返回頂部等等小特性。

那麼這些功能是如何實現的呢。這裡將為大家提供一些快速使用的萬能程式碼。

(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;
        });
})();
在看看測試頁面吧。 

<!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>返回頂部按鈕</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：




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