三：JS脚本

    // ==UserScript==
    // @name         页面自动滚动
    // @description  通过使用快捷键实现页面自动滚动
    // @match        *://*/*
    // @grant        none
    // ==/UserScript==

    (function() {        'use strict';           
     let speed = 0;           
     let speed_num = 1.5;  // 修改这个调整滚动速度
            
            let getScrollTop = () => {                var scrollTop = 0,
                    bodyScrollTop = 0,
                    documentScrollTop = 0;                if (document.body) {
                    bodyScrollTop = document.body.scrollTop;
                }                if (document.documentElement) {
                    documentScrollTop = document.documentElement.scrollTop;
                }
                scrollTop = (bodyScrollTop - documentScrollTop > 0) ?
                 bodyScrollTop : documentScrollTop;             
                   return scrollTop;
            }    
            let getWindowHeight = () => {                var windowHeight = 0;               
             if (document.compatMode == 'CSS1Compat') {
                    windowHeight = document.documentElement.clientHeight;
                } else {
                    windowHeight = document.body.clientHeight;
                }                return windowHeight;
            }           
            let getScrollHeight = () => {                var scrollHeight = 0,
                    bodyScrollHeight = 0,
                    documentScrollHeight = 0;                if (document.body) {
                    bodyScrollHeight = document.body.scrollHeight;
                }                if (document.documentElement) {
                    documentScrollHeight = document.documentElement.scrollHeight;
                }
                scrollHeight = (bodyScrollHeight - documentScrollHeight > 0) ?
                 bodyScrollHeight : documentScrollHeight;      
                          return scrollHeight;
            }           
            setInterval(() => {               
             let bottomFlag = (getScrollTop() + getWindowHeight() == getScrollHeight()) ? true : false;  
                          let topFlag = (getScrollTop() == 0) ? true : false;            
                              if (bottomFlag || topFlag) {
                    speed = 0;
                } else {                    document.documentElement.scrollTop += speed;
                }
            }, 5)     
            document.onkeydown = (e) => {
                e = event || window.event;                // 同时按上键与alt键向上滚动
                if (e && e.keyCode == 38 && e.altKey) { 
                    let bottomFlag = (getScrollTop() + getWindowHeight() == getScrollHeight()) ? true : false;             
                           if (bottomFlag) {                        document.documentElement.scrollTop += -1;
                    }
                    speed -= speed_num;
                }                // 同时按下键与alt键向下滚动
                if (e && e.keyCode == 40 && e.altKey) { 
                    let topFlag = (getScrollTop() == 0) ? true : false;                 
                       if (topFlag) {                        document.documentElement.scrollTop += 1;
                    }
                    speed += speed_num;
                }                // 同时按 CTRL + ALT 键停止滚动
                if (e && e.altKey && e.ctrlKey) {
                    speed = 0;
                }
            }            // 单击页面停止滚动
            document.onclick = () => {
                speed = 0;
            }            // 滑动滚轮页面停止滚动
            document.onmousewheel = () => {
                speed = 0;
            }            document.addEventListener("DOMMouseScroll", () => {
                speed = 0;
            })
    })();