javascript圓盤抽獎程序實現原理和完整代碼例子

2019-11-20 14:57:22

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效果預覽：

一、模擬抽獎的實現過程

旋轉原理：當支持CSS3屬性采用transform: rotate（角度deg）設置,當角度為正數時順時針旋轉，當為負數時逆時針旋轉。如果是IE8及其以下，采用采用絕對定位設置top和left，模擬角度旋轉。

run方法，參數angle指角度

復制代碼代碼如下:

function run(angle) {
                    if (isIE) {
                        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) {
                        target.style.MozTransform = "rotate(" + angle + "deg)";
                    } else if (target.style.OTransform !== undefined) {
                        target.style.OTransform = "rotate(" + angle + "deg)";
                    } else if (target.style.webkitTransform !== undefined) {
                        target.style.webkitTransform = "rotate(" + angle + "deg)";
                    } else {
                        target.style.transform = "rotate(" + angle + "deg)";
                    }
                }

模擬轉盤加速，勻速和減速。當角度小于某個數值時，讓其處于加速此處采用1.01的系數作為加速度，當大于某個數值時處于高速勻速狀態，當角度大于設置的最大數值時，讓其減速采用系數為0.99。設置負數作為減速的值（即變量 tmp），隨即獲取負360中的值（即變量 m），當大于這個值時，轉盤停止。

復制代碼代碼如下:

var tmp = -900;
                var m = -parseInt(Math.random() * 360);
                timer = setInterval(function () {
                    if (i > 3000) {
                        tmp = parseInt(tmp * 0.99);
                        if (tmp > m) {
                            tmp = m;
                            clearInterval(timer);
                            msg(m);
                        }
                        run(tmp);
                    }
                    else if (i > 1000) {
                        i = i + 45;
                        run(i);
                    }
                    else {
                        i = parseInt((i + 1) * 1.01);
                        run(i);
                    }
                }, 50);

啟動抽獎和重新設置抽獎

復制代碼代碼如下:

<input id="test" type="button" value="抽獎" />
<input id="restart" style="display: none;" type="button" value="再抽一次" />
m$('test').onclick = function () {
                m$('test').style.display = "none";
                showMsg();
            }

m$('restart').onclick = function () {
m$('restart').style.display = "none";

                if (isIE) {
                    m$("demo").style.top = "0px";
                    m$("demo").style.left = "0px";
                } else if (m$("demo").style.MozTransform !== undefined) {
                    m$("demo").style.MozTransform = 'rotate(0deg)';
                } else if (m$("demo").style.OTransform !== undefined) {
                    m$("demo").style.OTransform = 'rotate(0deg)';

                } else if (m$("demo").style.webkitTransform !== undefined) {
                    m$("demo").style.webkitTransform = 'rotate(0deg)';
                } else {
                    m$("demo").style.transform = 'rotate(0deg)';
                }

                m$('test').style.display = "block";
                i = 0;
            }

二、完整代碼demo:

復制代碼代碼如下:

<!DOCTYPE html>
<html>
<head>
    <title>抽獎</title>
    <style type="text/css">
        #container{width: 400px;height: 400px;position: relative;margin: 0 auto;}
        #demo{position: absolute;filter: progid:DXImageTransform.Microsoft.Matrix(sizingmethod="auto expand");}
    </style>
</head>
<body style="height: 1000px;">
    <div id="container">
        <div id="demo">
            <img alt="" src="http://files.VeVB.COm/file_images/article/201406/20146394819279.png?20145394926" width="400" height="400" />
        </div>
    </div>
    <input id="test" type="button" value="抽獎" />
    <input id="restart" style="display: none;" type="button" value="再抽一次" />
    <div id="msg">
    </div>
    <script type="text/javascript">
        var m$ = function (id) { return document.getElementById(id); }
        var ua = navigator.userAgent;
        var isIE = /msie/i.test(ua) && !window.opera;

        window.onload = function () {
            m$('test').onclick = function () {
                m$('test').style.display = "none";
                showMsg();
            }

m$('restart').onclick = function () {
m$('restart').style.display = "none";

                m$('test').style.display = "block";
                i = 0;
            }
        }
    </script>
</body>
</html>

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