为什么我的当前值会比目标值差1px
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<style>
ul li{
width: 100px;
height: 100px;
background: yellow;
border: 1px solid #000;
list-style: none;
margin-bottom: 20px;
filter: alpha(opacity:30);
opacity: 0.3;
/* position: fixed;
right: 500px;
bottom: 300px; */
}
</style>
<body>
<ul>
<li id="li1"></li>
<!-- <li id="li2"></li> -->
</ul>
<script>
window.onload = function(){
// var li = document.getElementsByTagName('li');
// for(var i=0;i<li.length;i++){
// //给每个li配一个定时器
// li[i].timer
// li[i].onmouseover= function(){
// start(this,400);
// };
// li[i].onmouseout= function(){
// start(this,200);
// }
// };
var li1 = document.getElementById('li1');
var li2 = document.getElementById('li2');
li1.onmouseover = function(){
start(li1,{width:300},function(){
alert(1)
});
};
li1.onmouseout = function(){
start(this,{width:100});
};
// li2.onmouseover = function(){
// start(this,'height',400);
// };
// li2.onmouseout = function(){
// start(this,'height',100);
// };
}
//获取样式
function getStyle(obj,attr){
if(obj.currentStyle){
return obj.currentStyle[attr];
}else{
return getComputedStyle(obj,false)[attr];
}
}
function start(obj,json,fn){
var flag = true;
clearInterval(obj.timer);
obj.timer = setInterval(function(){
for(var attr in json){
var cur = 0;
if(attr=='opacity'){
cur = Math.round(parseFloat(getStyle(obj,attr))*100);
}else{
cur = parseInt(getStyle(obj,attr));
};
var speed = (json[attr]-cur)/8;
speed = speed>0?Math.ceil(speed):Math.floor(speed);
if(json[attr]!=cur){
flag = false;
// console.log(flag);
console.log('目标值'+json[attr]);
console.log('现在值'+cur)
};
//obj.style.width===obj.style[width],这里要写成这样！！！
if(attr=='opacity'){
obj.style.filter = 'alpha(opacity:'+(cur+speed)+')';
obj.style.opacity = (cur+speed)/100;
}else{
obj.style[attr] = cur+speed+'px';
};
};
if(flag){
clearInterval(obj.timer);
if(fn){
fn()
};
};
},30)
}
</script>
</body>
</html>
