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Javascript simulates scroll scrolling effect script page 1/2_javascript skills

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2016-05-16 19:00:451110browse

Code

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 
<html> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 
<title>Insert title here</title> 
<script type="text/javascript"> 
var oEventUtil = new Object(); 
oEventUtil.addEventHandler = function (oTarget,sType,fnDo){ 
    if(oTarget.addEventListener){ 
        oTarget.addEventListener(sType,fnDo,false) 
    } 
    if(oTarget.attachEvent){ 
        oTarget.attachEvent("on"+sType,fnDo) 
    } 
    else{ 
        oTarget["on"+sType] = fnDo; 
    } 
} 
oEventUtil.removeEventHandler = function (oTarget,sType,fnDo){ 
    if(oTarget.removeEventListener){ 
        oTarget.removeEventListener(sType,fnDo,false) 
    } 
    if(oTarget.detachEvent){ 
        oTarget.detachEvent("on"+sType,fnDo) 
    } 
    else{ 
        oTarget["on"+sType] = null; 
    } 
} 
oEventUtil.getEvent = function() { 
if (window.event) { 
return this.formatEvent(window.event); 
} else { 
return oEventUtil.getEvent.caller.arguments[0]; 
} 
} 
oEventUtil.formatEvent = function (oEvent) 
{ 
oEvent.pageY = oEvent.clientY + document.body.scrollTop; 
return oEvent; 
} 
function areaScroll(){ 
    var scroll_hand_top = parseInt(scrollup.offsetHeight); 
var scroll_hand_bottom = parseInt(category_list.offsetHeight) - parseInt(scrolldown.offsetHeight) - parseInt(scroll_hand.offsetHeight); 
    category_list.scrollTop = (parseInt(category_list.scrollHeight)-parseInt(category_list.offsetHeight) + parseInt(scrollup.offsetHeight))*(parseInt(scroll_hand.style.top)-parseInt(scrollup.offsetHeight))/(parseInt(scroll_hand_bottom)-parseInt(scrollup.offsetHeight))-parseInt(scrollup.offsetHeight); 

} 
function clickNarrowup(){ 
var oEvent = oEventUtil.getEvent(); 
    var scroll_hand_top = parseInt(scrollup.offsetHeight); 
    var scroll_hand_bottom = parseInt(category_list.offsetHeight) - parseInt(scrolldown.offsetHeight) - parseInt(scroll_hand.offsetHeight); 
     
    if(parseInt(scroll_hand.offsetTop) <= parseInt(scroll_hand_bottom) && parseInt(scroll_hand.offsetTop) >= parseInt(scroll_hand_top)){ 
        scroll_hand.style.top = parseInt(scroll_hand.offsetTop) - 10 +"px"; 
        if(parseInt(scroll_hand.style.top) >= parseInt(scroll_hand_bottom)){ 
            scroll_hand.style.top = parseInt(scroll_hand_bottom)+"px"; 
        } 
        if(parseInt(scroll_hand.style.top)<=parseInt(scroll_hand_top)){ 
            scroll_hand.style.top = parseInt(scroll_hand_top)+"px"; 
        } 
        areaScroll();         
    }     
} 
function clickNarrowdown(){ 
var oEvent = oEventUtil.getEvent(); 
    var scroll_hand_top = parseInt(scrollup.offsetHeight); 
var scroll_hand_bottom = parseInt(category_list.offsetHeight) - parseInt(scrolldown.offsetHeight) - parseInt(scroll_hand.offsetHeight); 
    if(parseInt(scroll_hand.offsetTop) <= parseInt(scroll_hand_bottom) && parseInt(scroll_hand.offsetTop) >= parseInt(scroll_hand_top)){ 
        scroll_hand.style.top = parseInt(scroll_hand.offsetTop) + 10 +"px"; 
        if(parseInt(scroll_hand.style.top) > parseInt(scroll_hand_bottom)){ 
            scroll_hand.style.top = parseInt(scroll_hand_bottom)+"px"; 
        } 
        if(parseInt(scroll_hand.style.top)<parseInt(scroll_hand_top)){ 
            scroll_hand.style.top = parseInt(scroll_hand_top)+"px"; 
        } 
        areaScroll(); 
    } 
} 
function mousedown(e){ 
var oEvent = oEventUtil.getEvent(); 
y = parseInt(oEvent.pageY) - parseInt(scroll_hand.offsetTop); 
oEventUtil.addEventHandler(scroll_hand, "mousemove", mousemove); 
oEventUtil.addEventHandler(scroll_hand, "mouseup", mouseup); 
oEventUtil.addEventHandler(scroll_hand, "mouseout", mouseout); 
} 
function mousemove(e){ 
    var oEvent = oEventUtil.getEvent(); 
    var scroll_hand_top = parseInt(scrollup.offsetHeight); 
    var scroll_hand_bottom = parseInt(category_list.offsetHeight) - parseInt(scrolldown.offsetHeight) - parseInt(scroll_hand.offsetHeight); 
     
    if(parseInt(scroll_hand.offsetTop) <= parseInt(scroll_hand_bottom) && parseInt(scroll_hand.offsetTop) >= parseInt(scroll_hand_top)){ 
        scroll_hand.style.top = parseInt(oEvent.pageY) - y + "px"; 
        if(parseInt(scroll_hand.style.top) > parseInt(scroll_hand_bottom)){ 
            scroll_hand.style.top = parseInt(scroll_hand_bottom)+"px"; 
        } 
        if(parseInt(scroll_hand.style.top)<parseInt(scroll_hand_top)){ 
            scroll_hand.style.top = parseInt(scroll_hand_top)+"px"; 
        } 
        areaScroll(); 
    } 
} 
function mouseup(e){ 
    oEventUtil.removeEventHandler(scroll_hand,"mousemove",mousemove); 
    oEventUtil.removeEventHandler(scroll_hand,"mouseup",mouseup); 
} 
function mouseout(e){ 
    oEventUtil.removeEventHandler(scroll_hand,"mousemove",mousemove); 
    oEventUtil.removeEventHandler(scroll_hand,"mouseout",mouseout); 
} 
function displayScrollbar(){ 
    if(category_list.scrollHeight > category_list.offsetHeight){ 
        category_scroll.style.display="block"; 
    } 
    else{category_scroll.style.display="none";} 
} 
window.onload = function () { 
//var category_scroll = document.getElementById("category_scroll"); 
    //var scroll_hand = document.getElementById("scroll_hand"); 
    //var scrollup = document.getElementById("scrollup"); 
    //var scrolldown = document.getElementById("scrolldown"); 
    //var category_list = document.getElementById("category_list"); 
category_list.scrollTop = 0; 
displayScrollbar(); 
oEventUtil.addEventHandler(scroll_hand,"mousedown",mousedown); 
    oEventUtil.addEventHandler(scrollup,"click",clickNarrowup); 
    oEventUtil.addEventHandler(scrolldown,"click",clickNarrowdown); 
} 
</script> 
<style type="text/css"> 
.category_list{width:200px;border:solid 1px #666666;height:300px;position:relative;} 
#category_list{list-style:none;margin:0;padding:0;padding-left:20px;overflow:hidden;height:298px;} 
#category_scroll{height:298px;width:15px;border:green solid 1px;position:absolute;right:0;top:0;font-size:12px;cursor:hand;} 
#scrollup{height:15px;width:15px;border:green solid 1px;} 
#scroll_hand{height:100px;width:15px;border:green solid 1px;position:absolute;} 
#scrolldown{height:15px;width:15px;border:green solid 1px;position:absolute;bottom:0;} 
</style> 
</head> 
<body> 
<div class="category_list"> 
<ul id="category_list"> 
    <li>1something</li> 
    <li>2something</li> 
    <li>3something</li> 
    <li>4something</li> 
    <li>5something</li> 
    <li>6something</li> 
    <li>7something</li> 
    <li>8something</li> 
    <li>9something</li> 
    <li>10something</li> 
    <li>11something</li> 
    <li>12something</li> 
    <li>13something</li> 
    <li>14something</li> 
    <li>15something</li> 
    <li>16something</li> 
    <li>17something</li> 
    <li>18something</li> 
    <li>19something</li> 
    <li>20something</li> 
    <li>21something</li> 
    <li>22something</li> 
    <li>23something</li> 
    <li>24something</li> 
    <li>25something</li> 
    <li>26something</li> 
    <li>27something</li> 
    <li>28something</li> 
    <li>29something</li> 
    <li>30something</li> 
</ul> 
<div id="category_scroll"> 
    <div id="scrollup">上</div> 
            <div id="scroll_hand">滚动滚动滚动</div> 
            <div id="scrolldown">下</div> 
            <script type="text/javascript"> 
                var category_scroll = document.getElementById("category_scroll"); 
                var scroll_hand = document.getElementById("scroll_hand"); 
                var scrollup = document.getElementById("scrollup"); 
                var scrolldown = document.getElementById("scrolldown"); 
                var category_list = document.getElementById("category_list"); 
            </script> 
        </div> 
     </div> 
</body> 
</html>

Now there is a problem: when the scroll bar is clicked, the up and down keys of the keyboard are triggered to control the up and down scrolling. However, in general, keyboard events seem to only work for Form form objects and Winsow form objects (except IE), so how should we write when creating event handling functions?
oEventUtil.addEventHandler(category_hand,"keyup",test) seems not to work. After all, category_hand represents a DIV. The
test() function is as follows:
function test(){
//alert("RUN");
var oEvent = oEventUtil.getEvent();
if(oEvent.keyCode==38){
alert("UP");
clickNarrowup();
}
if(oEvent.keyCode==40){
clickNarrowdown();
alert("DOWN");
}
}
Please help me answer this question.

Question 2: In this code, when defining the variable, I inserted the code in the middle of the HTML to obtain the object. If this code is inserted into the window.onload function, then it is very likely that At this time, these objects have not been loaded and cannot be read and a program error will occur. The question is, if I want to completely:
4ec11beb6c39d0703d1751d203c17053
var category_scroll = document.getElementById("category_scroll");
var scroll_hand = document.getElementById("scroll_hand");
var scrollup = document.getElementById("scrollup");
var scrolldown = document.getElementById("scrolldown");
var category_list = document.getElementById("category_list");
2cacc6d41bbb37262a98f745aa00fbf0 What is the best way to deal with the introduction of
to 93f0f5c25f18dab9d176bd4f6de5d30e?
The solution given by the blueidea moderator

1. Keyboard events should be added to the window for unified deployment and processed according to the category_hand activation status.
2. Put it in the function and wait until the page is loaded before executing it.
1. "Keyboard events should be added to the window for unified deployment, and processed according to the category_hand activation status" is the strategy to realize your sentence:
"When the scroll bar is clicked, trigger the up and down keys of the keyboard to control Scroll up and down”
When category_hand is clicked, a variable is set to 1, indicating that it is activated. When another mouse button event occurs in the web page, it will be deactivated.
A function responds to the keyboard event of the window object. If the category_hand is activated when the keyboard event occurs, the relevant code will be executed.

2. Get the page element object. Now everyone generally uses the $() function: 

function $(id) { 
return 
document.getElementById(id); 
}
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