<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>Document</title>
<style>
* {
margin: 0;
padding: 0;
box-sizing: border-box;
}
.box {
width: 200px;
height: 200px;
background: skyblue;
position: absolute;
left: 50%;
top: 50%;
transform: translate(-50%, -50%);
bottom: 0;
}
.bd {
text-align: center;
}
</style>
</head>
<body>
<div class="bd">
<div class="box"></div>
<button class="changeWidth">变宽</button>
<button class="changeHeight">变高</button>
<button class="changeColor">变色</button>
<button class="changeHide">隐藏</button>
<button class="back">重置</button>
</div>
<script>
var changeWidth= document.getElementsByClassName('changeWidth')[0].onclick=function(){
document.getElementsByClassName('box')[0].style.width=300+'px'
};
document.getElementsByClassName('changeHeight')[0].onclick=function(){
document.getElementsByClassName('box')[0].style.height=300+'px'
};
document.getElementsByClassName('changeColor')[0].onclick=function(){
document.getElementsByClassName('box')[0].style.background="blue"
};
document.getElementsByClassName('changeHide')[0].onclick=function(){
document.getElementsByClassName('box')[0].style.display="none"
};
document.getElementsByClassName('back')[0].onclick=function(){
document.getElementsByClassName('box')[0].style.cssText=""
document.getElementsByClassName('box')[0].style.display="block"
};
</script>
</body>
</html>
像这样一个个的改变style太过于麻烦，我们可以将代码精简，用循环来减少代码的重复
<script>
window.onload = function() {
let btn = document.getElementsByTagName('button');
let odiv = document.getElementsByClassName('box')[0];
let change = ['width', 'height', 'background', 'display', 'display'];
let value = ['300px', '300px', 'blue', 'none', 'block']
for(let i = 0; i < btn.length; i++) {
btn[i].onclick = function() {
if(i==4){
odiv.style.cssText = ""
}
odiv.style[change[i]] = value[i]
}
}
}
</script>
代码的发展必然是越来越精简 运行速度越来越快的 所以平时写完代码后要用心观察 思考如何精简这样才是个合格的程序猿
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