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JavaScript determines whether a picture is loaded in three ways---turn

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Three ways JavaScript determines whether a picture is loaded

Sometimes you need to get the size of the picture, which needs to be done after the picture is loaded. There are three ways to achieve this, as described below.

First, the Load event
12345678910111213141516 <!DOCTYPE HTML>    <meta charset="utf-8">    <title>img - load event</title><body>    "img1"src="http://pic1.win4000.com/wallpaper/f/51c3bb99a21ea.jpg">    <p id="p1">loading...</p>    <script type="text/javascript">        img1.onload = function() {            p1.innerHTML = ‘loaded‘        }    </script></body>

Test, all browsers show "loaded", indicating that all browsers support IMG's Load event.

I also tried the JS through the ID is also possible to use the OnLoad method.

document.getElementById ("Img1"). onload=function() {            var height = $ (' #img1 '). Height ();            alert (height);    }

But the jquery element is not the OnLoad method

// jquery Element---no    $ ("#img1"). onload=function() {            var height = $ (' #img1 '). Height ();            alert (height);    }

Ii. ReadyStateChange Events
123456789101112131415161718 <!DOCTYPE HTML>    <meta charset="utf-8">    <title>img - readystatechange event</title><body>    "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></body>

ReadyState for complete and loaded indicates that the picture has been loaded. The test Ie6-ie10 supports this event and is not supported by other browsers.

Third, the Complete property of img
123456789101112131415161718192021222324 <!DOCTYPE HTML>    <meta charset="utf-8">    <title>img - complete attribute</title><body>    "img1"src="http://pic1.win4000.com/wallpaper/f/51c3bb99a21ea.jpg">    <p id="p1">loading...</p>    <script type="text/javascript">        functionimgLoad(img, callback) {            vartimer = setInterval(function() {                if(img.complete) {                    callback(img)                    clearInterval(timer)                }            }, 50)        }        imgLoad(img1, function() {            p1.innerHTML(‘加载完毕‘)        })    </script></body>

Polling continuously monitors the complete property of IMG and, if true, indicates that the picture has been loaded and stopped polling. This property is supported by all browsers.

JavaScript determines whether a picture is loaded in three ways---turn

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