代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
img{
display:inline-block;
width:170px;
height:270px;
}
</style>
</head>
<body>
<img src="images/bright.jpg" alt="">
<script>
var img = document.getElementsByTagName('img')[0];
// 自定义 属性
var flag = true; // 假设 开关flag 值 true-亮 false-灭
img.onclick = function(){
if(flag){ // flag是否为true 是不是亮的
img.src = 'images/dark.jpg';
flag = false;
}else{
img.src = 'images/bright.jpg';
flag = true;
}
}
</script>
</body>
</html>
效果