window.onload = function(){

    var screenAnimateElements = {

        '.screen_1': [

            '.screen_1_text',

            '.screen_1_phone',

            '.screen_1_shadow',

        ],

        '.screen_2':[

            '.screen_2_head',

        ],

        为什么我在这里加了.screen_2而第一屏第二屏点击都没反应了

    };

    function setScreenAnimate(screenCls){

        var screen = document.querySelector(screenCls);//获取当前屏的元素

        var animateElements = screenAnimateElements[screenCls];//需要设置动画的元素

        var isSetAnimateClass = false;//是否有初始化子动画元素的样式

        var isAnimateDone = false;//当前屏幕所有子元素是done吗?

        screen.onclick = function(){

            //初始化动画,增加init

            if(isSetAnimateClass === false){

                //遍历所有动画元素

                for(var i = 0; i < animateElements.length; i++){

                    //获取当前动画元素的classNmae

                    var element = document.querySelector(animateElements[i]);

                    var baseCls = element.getAttribute('class');

                    //设置当前动画元素的classNmae,增加'_animate_init'

                    element.setAttribute('class',baseCls + ' ' + animateElements[i].substr(1) + '_animate_init' );

                }

                //当前动画元素样式已增加init,所以isSetAnimateClass = true;

                isSetAnimateClass = true;

                return;

            }

            //切换所有 animateElements  的   init → done

            if(isAnimateDone === false){

                for(var i = 0; i < animateElements.length; i++){

                    var element = document.querySelector(animateElements[i]);

                    var baseCls = element.getAttribute('class');

                    //设置当前动画元素的classNmae,把'_animate_init'替换成'_animate_done'

                    element.setAttribute('class',baseCls.replace('_animate_init','_animate_done'));

                }

                //当前动画元素样式已替换成done,所以isSetAnimateClass = true;

                isAnimateDone = true;

                return;

            }

            //切换所有 animateElements  的   done → init

            if(isAnimateDone === true){

                for(var i = 0; i < animateElements.length; i++){

                    var element = document.querySelector(animateElements[i]);

                    var baseCls = element.getAttribute('class');

                    element.setAttribute('class',baseCls.replace('_animate_done','_animate_init'));

                }

                isAnimateDone = false;

                return;

            }

        }

    }

    for(k in screenAnimateElements);

    setScreenAnimate(k);

}