<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>輪播圖</title>
<script>
var number = 1;
function fun() {;
number++;
document.getElementById("img");
if (number>3){
number = 1;
}
img.src = "../img/picture_"+number+".jpg";
}
setInterval(fun,3000);
</script>
</head>
<body>
<img src="../img/picture_1.jpg" width="100%" height="300px" id="img">
</body>
</html
將scrip標籤寫在img標籤之前，也可以獲取img對象，因爲先是將圖片加載出來，三秒鐘後定時器調用fun方法，再獲取img對象，此時圖片已經加載。