//主函数
var wyBannel = function() {
    var interv = 4000; //切换间隔时间
    var interv2 = 10; //切换速速
    var opac1 = 80; //文字背景的透明度
    var source = "wyBannel" //焦点轮换图片容器的id名称
    //获取对象
    function getTag(tag, obj) {
        if (obj == null) {
            return document.getElementsByTagName(tag)
        } else {
            return obj.getElementsByTagName(tag)
        }
    }
    function getid(id) {
        return document.getElementById(id)
    }
    var opac = 0,
    j = 0,
    t = 63,
    num, scton = 0,
    timer, timer2, timer3;
    var id = getid(source);
    id.removeChild(getTag("div", id)[0]);
    var li = getTag("li", id);
    var div = document.createElement("div");
    var span = document.createElement("span");
    var button = document.createElement("div");
    button.className = "button";
    for (var i = 0; i < li.length; i++) {
        var a = document.createElement("a");
        a.innerHTML = i + 1;
        a.onclick = function() {
            clearTimeout(timer);
            clearTimeout(timer2);
            clearTimeout(timer3);
            j = parseInt(this.innerHTML) - 1;
            scton = 0;
            t = 63;
            opac = 0;
            fadeon();
        };
        a.className = "b1";
        a.onmouseover = function() {
            this.className = "b2"
        };
        a.onmouseout = function() {
            this.className = "b1";
            sc(j)
        };
        button.appendChild(a);
    } 
	//控制图层透明度
    function alpha(obj, n) {
        if (document.all) {
            obj.style.filter = "alpha(opacity=" + n + ")";
        } else {
            obj.style.opacity = (n / 100);
        }
    } //控制焦点按钮
    function sc(n) {
        for (var i = 0; i < li.length; i++) {
            button.childNodes[i].className = "b1"
        };
        button.childNodes[n].className = "b2";
    }
    id.className = "d1";
    div.className = "d2";
    id.appendChild(div);
    id.appendChild(button); 
	
	//渐显
    var fadeon = function() {
        opac += 5;
        div.innerHTML = li[j].innerHTML;
        span.innerHTML = getTag("img", li[j])[0].alt;
        alpha(div, opac);
        if (scton == 0) {
            sc(j);
            num = -2;
            scrolltxt();
            scton = 1
        };
        if (opac < 100) {
            timer = setTimeout(fadeon, interv2)
        } else {
            timer2 = setTimeout(fadeout, interv);
        };
    } 
	
	//渐隐
    var fadeout = function() {
        opac -= 5;
        div.innerHTML = li[j].innerHTML;
        alpha(div, opac);
        if (scton == 0) {
            num = 2;
            scrolltxt();
            scton = 1
        };
        if (opac > 0) {
            timer = setTimeout(fadeout, interv2)
        } else {
            if (j < li.length - 1) {
                j++
            } else {
                j = 0
            };
            fadeon()
        };
    }
	
	//滚动文字
    var scrolltxt = function() {
        t += num;
        span.style.marginTop = t + "px";
        if (num < 0 && t > 3) {
            timer3 = setTimeout(scrolltxt, interv2)
        } else if (num > 0 && t < 62) {
            timer3 = setTimeout(scrolltxt, interv2)
        } else {
            scton = 0
        }
    };
    fadeon();
} //初始化
//window.onload = wyBannel;