Js什么时候修改class
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
<script>
window.onload = function (){
var oBtn1 = document.getElementById('btn1');
var oBtn2 = document.getElementById('btn2');
var oBtn3 = document.getElementById('btn3');
var oBtn4 = document.getElementById('btn4');
var oP = document.getElementById('p1');
var num = 14;
oBtn1.onclick = function (){
num -= 2;
oP.style.fontSize = num + 'px';
// JS 不允许出现"-"
// padding-top paddingTop
// margin-left marginLeft
};
oBtn2.onclick = function (){
// num = num + 2;
num += 2;
oP.style.fontSize = num + 'px';
// JS 不允许出现"-"
};
oBtn3.onclick = function (){
// oP.class = 'red';
// class => className
oP.className = 'red';
};
oBtn4.onclick = function (){
// oP.class = 'red';
// class => className
oP.className = 'yellow';
};
};
</script>
<style>
.red { width:400px; border:10px solid #333; background:red; padding:20px; color:yellow; }
.yellow { width:500px; border:5px solid #333; background:yellow; padding:10px; color:red; }
</style>
</head>
<body>
<input id="btn1" type="button" value="-" />
<input id="btn2" type="button" value="+" />
<input id="btn3" type="button" value="红" />
<input id="btn4" type="button" value="黄" />
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</body>
</html>
