<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<img id="img1" src="http://pic1.win4000.com/wallpaper/f/51c3bb99a21ea.jpg" alt="">
<script>
// 方法一：圖片已經(jīng)下載完
document.getElementById('img1').onload = function(e){
e.stopPropagation();
alert(1);
}
</script>
</body>
</html>

二.判斷img對(duì)象（DOM）的complete屬性

當(dāng)img加載完成之后，complete對(duì)象屬性將變?yōu)閠rue，代碼示例如下：

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<img id="img1" src="http://pic1.win4000.com/wallpaper/f/51c3bb99a21ea.jpg" alt="">
<script>
// 方法二：img的complate屬性
var timer = setInterval(function(){
if (document.getElementById('img1').complete){
clearInterval(timer);
alert(1);
console.log(document.getElementById('img1').complete)
}
}, 10);
</script>
</body>
</html>

親測(cè)該方法同樣可兼容所有瀏覽器

三.onreadystatechange事件

在ie下，img對(duì)象與xhr對(duì)象一樣具有onreadystatechange事件，可以通郭建廷該事件判斷圖片是否加載完成，代碼示例如下：

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<img id="img1" src="http://pic1.win4000.com/wallpaper/f/51c3bb99a21ea.jpg" alt="">
<script>
document.getElementById('img1').onreadystatechange = function() {
if(document.getElementById('img1').readyState=="complete"||document.getElementById('img1').readyState=="loaded"){
alert(1);
}
}
</script>
</body>
</html>

該方法僅在ie下可用

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