javascript 代码解释

゛白昼怎懂夜的黑ヽ 发布于 2012/03/18 09:14
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最近在学习javascript,就在网上找了这段代码,是用来元素旋转的,但是看到run函数的时候就看不懂了
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title> ImageRotation </title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<style type="text/css">
#demo { cursor:pointer; position:absolute;filter:progid:DXImageTransform.Microsoft.Matrix(sizingmethod="auto expand");}
</style>
</head>
<body>
<div id="container" style="width:500px;height:350px;position:relative;margin:0 auto">
    <div id="demo">
        <img src="http://img.baidu.com/img/logo-zhidao.gif" />
    </div>
</div>
<script>
var Img = function() {
    var T$ = function(id) { return document.getElementById(id); }
    var ua = navigator.userAgent,
        isIE = /msie/i.test(ua) && !window.opera;
    var i = 0, sinDeg = 0, cosDeg = 0, timer = null ;
    var rotate = function(target, degree) {
        target = T$(target);
        var orginW = target.clientWidth, orginH = target.clientHeight;
            clearInterval(timer);
        function run(angle) {
            if (isIE) { // IE
                cosDeg = Math.cos(angle * Math.PI / 180);
                sinDeg = Math.sin(angle * Math.PI / 180);
                with(target.filters.item(0)) {
                    M11 = M22 = cosDeg; M12 = -(M21 = sinDeg); 
                }
                target.style.top = (orginH - target.offsetHeight) / 2 + 'px';
                target.style.left = (orginW - target.offsetWidth) / 2 + 'px';
            } else if (target.style.MozTransform !== undefined) {  // Mozilla
                target.style.MozTransform = 'rotate(' + angle + 'deg)';
            } else if (target.style.OTransform !== undefined) {   // Opera
                target.style.OTransform = 'rotate(' + angle + 'deg)';
            } else if (target.style.webkitTransform !== undefined) { // Chrome Safari
                target.style.webkitTransform = 'rotate(' + angle + 'deg)';
            } else {
                target.style.transform = "rotate(" + angle + "deg)";
            }
        }
        
        timer = setInterval(function() {
            i += 10;
            run(i);
            if (i > degree - 1) {
                i = 0;
                clearInterval(timer);
            } 
        }, 10); 
    }
    return {rotate: rotate}
}();
window.onload = function() {
    Img.rotate('demo', 360);
    document.getElementById('demo').onclick = function() {
        Img.rotate('demo', 360);
    }
}
</script>
</body>
</html> 
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Jason阿坚
Jason阿坚
数学计算和修改样式
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