js animation learning (3)

5. Multi-object widening



It should be noted that since there are more objects, each object needs to be equipped with a timer, otherwise if there is only one timer, When the mouse slides quickly between different objects, different objects will compete for each other. Therefore, obj must be added before timer.

function changeWidth(obj,target) {//元素，目标值
     clearInterval(obj.timer);//清除定时器防止嵌套调用
     obj.timer=setInterval(function () {//设置定时器
         var speed=(target-obj.offsetWidth)/8;//定义缓冲速度，目标值减当前值
         speed=speed>0?Math.ceil(speed):Math.floor(speed);//缓冲速度一定要取整
         if (obj.offsetWidth==target) {//判断物体当前宽度和目标值的关系，如果达到目标清除定时器
             clearInterval(obj.timer);    
         } else {
             obj.style.width=obj.offsetWidth+speed+'px';
         }
     },30)
 }

Example: Use 3 li as an example:

<style type="text/css">
     *{
         margin: 0;
         padding: 0;
     }
     ul li{
         width: 200px;
         height: 100px;
         background: yellow;
         margin-bottom: 20px;
     }
 </style>

<script type="text/javascript">
     window.onload=function(){
         var ob=document.getElementsByTagName(&#39;li&#39;);//一共3个li
         for (var i = 0; i < ob.length; i++) {
             ob[i].timer=null;//避免鼠标在他们仨快速移动时他们竞争定时器
             ob[i].onmouseover=function(){
                 changeWidth(this,400);
             }
             ob[i].onmouseout=function(){
                 changeWidth(this,200);
             }
         }
     }
 </script>

This parameter refers to the object itself. The difference from the previous times is that the timer clearing this time needs to be cleared separately for each li.



6. Multi-object transparency

When it comes to transparency, you must pay attention to browser compatibility issues. Also, the initial value of transparency cannot be set like the previous initial value of transparency for a single object. The initial value of transparency for multiple objects must be set separately, and each object has an initial value.

function changeOpacity(obj,speed,target) {
     clearInterval(obj.timer);//清除定时器，避免嵌套调用
     obj.timer=setInterval(function () {
         if (obj.alpha==target) {//如果透明度达到目标值，清除定时器
             clearInterval(obj.timer);
         } else {//当前透明度加上透明度变化的速度
             obj.alpha=obj.alpha+speed;
             obj.style.filter='alpha(opacity:'+obj.alpha+')';//IE浏览器
             obj.style.opacity=obj.alpha/100;//火狐和谷歌
         }
     }, 30)
 }

Here are a few div examples:

<style type="text/css">
     *{
         margin: 0;
         padding: 0;
     }
     div{
         width: 200px;
         height: 200px;
         background: red;
         margin: 10px;
         float: left;
         filter: alpha(opacity:30);/*filter滤镜：不透明度,IE浏览器*/ 
         opacity: 0.3;/*火狐和谷歌*/
     }
 </style>

<div></div>
 <div></div>
 <div></div>
 <script type="text/javascript">
     window.onload=function(){
         var ob=document.getElementsByTagName(&#39;div&#39;);
         for (var i = 0; i < ob.length; i++) {
             ob[i].timer=null;
             ob[i].alpha=30;//每一个的透明度初值要分开设置
             ob[i].onmouseover=function(){
                 changeOpacity(this,10,100);//从30变到100
             }
             ob[i].onmouseout=function(){
                 changeOpacity(this,-10,30);//从100变回30
             }
         }
     }
 </script>

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