老师单单这段代码是不是只能将元素设置init动画，

var screenAnimateElements = {  '.screen-1' : [    '.screen-1__heading',    '.screen-1__phone',    '.screen-1__shadow',  ],  '.screen-2' : [    '.screen-2__heading',    '.screen-2__subheading',    '.screen-2__phone',    '.screen-2__point_i_1',    '.screen-2__point_i_2',    '.screen-2__point_i_3',  ],  '.screen-3' : [    '.screen-3__heading',    '.screen-3__phone',    '.screen-3__subheading',    '.screen-3__features',  ],  '.screen-4' : [    '.screen-4__heading',    '.screen-4__subheading',    '.screen-4__type__item_i_1',    '.screen-4__type__item_i_2',    '.screen-4__type__item_i_3',    '.screen-4__type__item_i_4',  ],  '.screen-5' : [     '.screen-5__heading',    '.screen-5__subheading',    '.screen-5__bg',  ]};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; // 是否有初始化子元素的样式  var isAnimateDone = false; // 当前屏幕下所有子元素的状态是DONE？  screen.onclick = function(){    //  初始化样式，增加init A A_init    if( isSetAnimateClass === false){        for(var i=0;i<animateElements.length;i++){            var element = document.querySelector(animateElements[i]);            var baseCls = element.getAttribute('class');            element.setAttribute('class',baseCls +' '+animateElements[i].substr(1)+'_animate_init');        }        isSetAnimateClass = true;        return ;    }    //  切换所有 animateElements 的  init -> done   A A_done    if(isAnimateDone === false){      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_init','_animate_done'));      }      isAnimateDone = true;      return ;    }    //  切换所有 animateElements 的  done -> init   A A_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);}