Js realizes Jingdong's delay-free menu effect (demo)

It’s the Dragon Boat Festival, there are so many people outside, and it’s so hot. I think I can stay at home and read MOOCs to enrich my experience. ...

This is a js to achieve JD.com’s delay-free menu effect. It feels very good and I would like to share it with everyone...

<span style="color: #000000">先来理清思路:<br>1.开发基本的菜单结构     

2.开发普通的二级菜单效果

3.假如延迟解决移动问题 
  切换子菜单时候，用setTimeout设置延迟

  debounce去抖技
  在事件被频繁触发是，只执行一次处理

4.解决延迟引入的新问题  
  跟踪鼠标的移动
  用鼠标当前位置，和鼠标上一次位置与子菜单上下边缘的三角形区域进行比较
  
  运用到向量
  二位向量叉乘公式
  用叉乘法判断点在三角形内</span>

最终效果：鼠标自然的移动和点击到子菜单
         切换时无延迟

Start the code below:

Develop basic Menu structure

nbsp;html><meta><title>京东菜单无刷新</title><script></script><script></script><script></script><style>.wrap{position:relative;width:200px;left:50px;top:50px;}ul{padding:15px;margin:9;list-style:none;background:#6c6669;color:#ffffff;border-right-width:0;}/*水平居中*/li{display:block;height:30px;line-height: 30px;padding-left:12px;cursor:pointer;font-size: 14px;position:relative;}/*鼠标移动上去的背景色*/li.active{background:#999395;}/*js可以很好地调用类，一般效果css实现就好*/li span:hover{color:#c81623;}/*隐藏的类*/.none{display: none;}/*二级菜单*/#sub{width:600px;position: absolute;border:1px solid #f7f7f7;background:#f7f7f7;box-shadow:2px 0 rgba(0,0,0,.3);left: 200px;top:0;box-sizing:border-box;margin: 0px;padding:10px;}.sub-content a{font-style:12px;color:#666;text-decoration:none;}.sub-content dd a{border-left:1px solid #e0e0e0;padding:0 1px;margin:4px 0;}.sub-content dl {overflow:hidden;}.sub-content dt{float: left;width:70px;font-weight: bold;clear:left;position:relative;}.sub-content dd {float: left;margin-left: 5px;border-top:1px solid #eee;margin-bottom: 5px;}.sub-content dt i{width:4px;height: 14px;font:400 9px/14px consolas;position: absolute;right:5px;top:5px;}</style><div>
<ul>
<li>
<span>家用电器</span>    </li>
<li>
<span>手机 / 运营商 / 数码</span>    </li>
<li>
<span>电脑办公 / 办公</span>    </li>
<li>
<span>家居 / 家具 / 家装 / 厨具</span>    </li>
<li>
<span>男装 / 女装 / 童装 / 内衣 </span>    </li>
<li>
<span>美妆个护 / 宠物 </span>    </li>
<li>
<span>女鞋 / 箱包 / 钟表 / 珠宝 </span>    </li>
<li>
<span>男鞋 / 运动 / 户外</span>    </li>
<li>
<span>汽车 / 汽车用品  </span>    </li>
</ul>
<div>
<div><dl>
<dt><a>电视<i>&gt</i></a></dt>
<dd>
<a>曲面电视</a><a>超薄电视</a><a>HDR电视</a><a>DLED电视</a>
</dd>
<dt><a>空调<i>&gt</i></a></dt>
<dd>
<a>挂壁式空调</a><a>柜式空调</a><a>中央空调</a><a>以旧换新</a>
</dd>
<dt><a>洗衣机<i>&gt</i></a></dt>
<dd>
<a>滚筒式洗衣机</a><a>洗烘一体机</a><a>波轮洗衣机</a><a>迷你洗衣机</a>
</dd>
</dl></div>
<div><dl>
<dt><a>手机通讯<i>&gt</i></a></dt>
<dd>
<a>手机</a><a>对讲机</a><a>以旧换新</a><a>手机维修</a>
</dd>
<dt><a>运营商<i>&gt</i></a></dt>
<dd>
<a>合约机</a><a>选号机</a><a>固定电话</a><a>办宽带</a>
</dd>
<dt><a>手机配件<i>&gt</i></a></dt>
<dd>
<a>手机壳</a><a>贴膜</a><a>手机存储卡</a><a>数据线</a>
</dd>
</dl></div>
<div><dl>
<dt><a>电脑整机<i>&gt</i></a></dt>
<dd>
<a>笔记本</a><a>游戏本</a><a>平板电脑</a>
</dd>
<dt><a>电脑配件<i>&gt</i></a></dt>
<dd>
<a>显示器</a><a>CPU</a><a>主板</a>
</dd>
<dt><a>外设产品<i>&gt</i></a></dt>
<dd>
<a>鼠标</a><a>键盘</a><a>键盘套餐</a>
</dd>
</dl></div>
<div><dl>
<dt><a>厨具<i>&gt</i></a></dt>
<dd>
<a>烹饪锅具</a><a>刀剪配件</a><a>厨房配件</a><a>水具酒具</a>
</dd>
<dt><a>家纺<i>&gt</i></a></dt>
<dd>
<a>床品套件</a><a>被子</a><a>枕芯</a><a>蚊帐</a>
</dd>
<dt><a>生活日用<i>&gt</i></a></dt>
<dd>
<a>收纳用品</a><a>雨伞雨具</a><a>净化除味</a><a>浴室用品</a>
</dd>
</dl></div>
<div><dl>
<dt><a>女装<i>&gt</i></a></dt>
<dd>
<a>商城同款</a><a>当季热卖</a><a>2017新品</a><a>连衣裙</a>
</dd>
<dt><a>男装<i>&gt</i></a></dt>
<dd>
<a>商城同款</a><a>当季热卖</a><a>2017新品</a><a>牛仔裤</a>
</dd>
</dl></div>
<div><dl>
<dt><a>面部护肤<i>&gt</i></a></dt>
<dd>
<a>补水保湿</a><a>卸妆</a><a>洁面</a>
</dd>
</dl></div>
</div>
</div><p style="text-align:justify;"><span style="font-family: 宋体"><span style="font-size: 16px; color: #ff0000">Solution to the 2nd and 3rd problems</span><br></span></p><div class="cnblogs_code"><pre class="brush:php;toolbar:false">$(document).ready(function(){var sub = $('#sub')var activeRowvar activeMenuvar timervar mouseInSub = falsesub.on('mouseenter',function(e){
        mouseInSub = true}).on('mouseleave',function(e){
        mouseInSub = false})var mouseTrack = []var moveHandler = function(e){
        mouseTrack.push({
            x:e.pageX,
            y:e.pageY
        })if(mouseTrack.length > 3){
            mouseTrack.shift()
        }
    }

    $('#test')
        .on('mouseenter',function(e){
            sub.removeClass('none')

            $(document).bind('mousemove',moveHandler)
        })
        .on('mouseleave',function(e){
            sub.addClass('none')if(activeRow){
                activeRow.removeClass('active')
                activeRow = null;
            }if(activeMenu){
                activeMenu.addClass('none')
                activeMenu = null;
            }//解绑$(document).unbind('mousemove',moveHandler)
        })

        .on('mouseenter','li',function(e){if(!activeRow){
                activeRow = $(e.target).addClass('acrive')
                activeMenu = $('#'+activeRow.data('id'))
                activeMenu.removeClass('none')return}//清除if(timer){
                clearTimeout(timer)
            }//鼠标当前坐标var  currMousePos = mouseTrack[mouseTrack.length - 1]//上次的坐标var leftCorner = mouseTrack[mouseTrack.length-2]var delay = needDelay(sub,leftCorner,currMousePos)if(delay){// 时间触发，设置一个缓冲期timer = setTimeout(function(){//判断if(mouseInSub){return}
                    activeRow.removeClass('active')
                    activeMenu.addClass('none')

                    activeRow = $(e.target)
                    activeRow.addClass('active')
                    activeMenu = $('#'+ activeRow.data('id'))
                    activeMenu.removeClass('none')

                    timer = null}, 300)
            }else{var prevActiveRow = activeRowvar prevActiveMenu = activeMenu

                activeRow = $(e.target)
                activeMenu = $('#' + activeRow.data('id'))

                prevActiveRow.removeClass('active')
                prevActiveMenu.addClass('none')

                activeRow.addClass('active')
                activeMenu.removeClass('none')
            }
        })
})

Solution to new problems introduced by delay

function sameSign(a,b){return (a ^ b) >= 0}function vector(a,b){return{
        x:b.x - a.x,
        y:b.y - a.y
    }
}function vectorProduct(v1,v2){return v1.x * v2.y - v2.x * v1.y
}function isPointInTrangle(p,a,b,c){var pa = vector(p,a)var pb = vector(p,b)var pc = vector(p,c)var t1 = vectorProduct(pa,pb)var t2 = vectorProduct(pb,pc)var t3 = vectorProduct(pc,pa)return sameSign(t1,t2) && sameSign(t2,t3)
} 

function needDelay(elem,leftCorner,currMousePos){var offset = elem.offset()var topLeft = {
        x:offset.left,
        y:offset.top
    }var bottomLeft = {
        x:offset.left,
        y:offset.top + elem.height()
    }return isPointInTrangle(currMousePos,leftCorner,topLeft,bottomLeft)
}

When you see this, it will be realized Jingdong’s no-delay menu effect, and also likes you, you can see it here.

#Once in The IT industry is as deep as the sea, which gives me the feeling that it is necessary to maintain a positive learning attitude. I use a blog to record my progress.

## If you have any questions, you can leave a message and we can discuss and make progress together.