window.addEventListener('load',function(){
    var arrow_l = document.querySelector('.arrow-l');
    var arrow_r = document.querySelector('.arrow-r');
    var focus = document.querySelector('.focus');
    focus.addEventListener('mouseenter',function(){
        arrow_l.style.display = 'block';
        arrow_r.style.display = 'block';
        clearInterval(timer);
        timer = null;
    })
    focus.addEventListener('mouseleave',function(){
        arrow_l.style.display = 'none';
        arrow_r.style.display = 'none';
        timer = setInterval(function(){
            arrow_r.click();
        },2000)
    })

    var ul = focus.querySelector('ul');
    for(var i = 0; i < ul.children.length; i++){
        var li = this.document.createElement('li');
        var ol = focus.querySelector('.circle');
        var focusWidth = focus.offsetWidth;
        li.setAttribute('index',i);
        ol.appendChild(li);
        li.addEventListener('click',function(){
            for(var i = 0; i < ol.children.length; i++){
                ol.children[i].className = '';
            }
            this.className = 'current';
            var index = this.getAttribute('index');
            num = index;
            circle = index;
            animate(ul,-index * focusWidth - 40 );
        })
    }
    ol.children[0].className = 'current';

    var first = ul.children[0].cloneNode(true);
    ul.appendChild(first);

    //右侧按钮事件
    var num = 0;
    var circle = 0;
    var flag = true; //这里的flag就是节流阀
    arrow_r.addEventListener('click',function(){
        if(flag){  //如果flag为真,就执行下面的,条件不写就是默认为真
            flag = false; //先关闭节流阀
            if(num == ul.children.length - 1){
                ul.style.left = -40;
                num = 0;
            }
            num++;
            animate(ul,-num * focusWidth-40,function(){ //添加一个function回调函数
                flag = true; //打开节流阀
            });
            circle++;
            if(circle == ol.children.length){
                circle = 0;
            }
            circleChange();
        }
    });





    //左侧按钮做法(这个按钮的节流阀跟上面一样写)
    arrow_l.addEventListener('click',function(){
        if(flag){
            flag = false;
            if(num == 0){
                num = ul.children.length - 1;
                ul.style.left = -num * focusWidth + 'px';
            }
            num--;
            animate(ul,-num * focusWidth-40,function(){
                flag = true;
            });
            circle--;
            if(circle < 0){
                circle = ol.children.length - 1;
            }
            circleChange();
        }
    });
    function circleChange(){
        for(var i = 0; i < ol.children.length; i++){
            ol.children[i].className = '';
        }
        ol.children[circle].className = 'current';
    }

    var timer = this.setInterval(function(){
        arrow_r.click();
    },2000);
})