js滚动到指定元素

1. 代码：

   <style>
   button{
       position: fixed;
       bottom: 0;
       right: 0;
   }
   </style>
   <button id="button">click to see</button>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>2</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>3</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <a id="ele" href="#">see me</a>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>3</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>1</p>
   <p>4</p>
   <p>1</p>
   <p>1</p>
   <script>
   var button = document.getElementsByTagName('button')[0]
   button.onclick = function(){
       clickToSee('ele')   
   }
   function clickToSee(id,time = 1){
       var c_top = document.body.scrollTop
       var ele = document.getElementById(id)
       var e_top = ele.offsetTop
       var diff = e_top - c_top
       var step = diff/100
       time = time/100*1000
       var o_flag
       if(diff>0){
           o_flag = true
       }else{
           o_flag = false
       }
       var timer = setInterval(function(){
           var c_flag
           diff -= step
           window.scrollBy(0,step)
           if(diff>0){
               c_flag = true
           }else{
               c_flag = false
           }
           if(!o_flag === c_flag){
               clearInterval(timer)
           }
           console.log(diff)
       },time)
   }
   </script>

2. 效果：