JS判断图片是否加载完成三种方式

<p id="p1"></p>
<img id="img1" src="../Images/1.jpg" />
<script>
    function imgLoad(img, callcack) {
        var timer = setInterval(function () {
            if (img.complete) {//判断图片是否加载完成
                callcack(img)
                clearInterval(timer);
            }
        }, 50);
    }
    imgLoad(img1, function () {
        p1.innerHTML = ‘加载完成‘;
    });
</script>

<p id="p1"></p>
<img id="img1" src="../Images/1.jpg" />
<img id="img2" />
<script>
    //证明complete 属性不仅可以判断图片是否加载成功，还可以判断图片是否已经在缓存中存在
    console.info(img1.complete)
    setTimeout(function () {
        if (img1.complete) {
            console.info(‘加载成功‘ + img1.src);
            img2.src = img1.src;
            if (img2.complete) {
                console.info(‘img2加载成功‘);
            }
        } else {

        }
    }, 100);
</script>

<p id="p1"></p>
<img id="img1" src="../Images/1.jpg" />
<script>
    //图片加载成功触发事件
    img1.onload = function () {
        alert(3);
        p1.innerHTML = "图片加载成功";
    }
</script>

<img id="img1" src="http://pic1.win4000.com/wallpaper/f/51c3bb99a21ea.jpg">
<p id="p1">loading...</p>
<script type="text/javascript">
    img1.onreadystatechange = function() {
        if(img1.readyState=="complete"||img1.readyState=="loaded"){
            p1.innerHTML = ‘readystatechange:loaded‘
        }
    }
</script>