第一步:编写manifest.json

{

“name”: “Back To Top”,

“description”: “返回顶部”,

“version”: “0.1”,

“content_scripts”: [ //在内容中加载js

{

  "matches": \["http://*/*"\],   //匹配页面,哪些页面需要显示

  "js": \["top.js"\]   //加载的js

}

],

“manifest_version”: 2,

“default_icon”: “icon_128.png”, //设置默认图片

“icons”: { “128”: “icon_128.png” } //图标

}

第二部:添加返回顶部的纯js

(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';

        }

        $(btnId).style.display = display;

    });

})();

第三步:打包上传