jquery production click can'back to top' button

In the previous article, click the button to return to the top part of the new function

• The button no longer appears at the bottom of the page. The button is fixed to the left or right at a distance from the bottom of the page.
  .ClickTop{ display: none; color:white; padding: 5px 8px; border-radius: 10px; background: purple; position:fixed; left: 20px; bottom: 50px; z-index:3; cursor: pointer; }
  2. When the visible area is on the first screen, there is no button. When the page is scrolled up a certain distance , The button appears.

  • Add an event after the page starts to scroll

    window.onscroll = scroll;
    
    function scroll(){
            
            }
    

  • Scroll distance> 1/2 of the visible area of ​​the window

    var ScrollLength = $(document).scrollTop(); //获取滚动距离
    

    var ViewHeight = $(window).height(); //获取可视区域的高度
    

3. Put together the final js

var Btn = $('.ClickTop');
Btn.click(function(){
    
    
  $('html,body').animate({
    
     scrollTop: 0 }, 500);         
})
window.onscroll = scroll;
function scroll(){
    
    
  var ScrollLength = $(document).scrollTop();
  var ViewHeight = $(window).height();
  //这样获取的是窗口可视区域的大小，如果改成body获取的是body的高度
  console.log('页面开始滚动');
  console.log(ViewHeight);
  console.log(ScrollLength);
// 判断滚动距离 超过0.5倍可视区域的高度
  if (ScrollLength > ViewHeight/2) {
    
    
    Btn.show();
  } else {
    
    
    Btn.hide();
  }
}

https://codepen.io/littlelittlepig/pen/xBgoYN For more code, please move to the
concise version of the demo and click to return to the top effect. Welcome to comment and correct