自动滚动获胜't animate为$('html，body'）.animate

更改

var a= document.getElementsByClassName('.IndexSection');

至

var a= $('.IndexSection');

并将offsetTop更改为offset().top

 $('html,body').animate({
      scrollTop: a.eq(i).offset().top
    });

整个代码是：

(function() {
  var delay = false;
  $(document).on('mousewheel DOMMouseScroll', function(event) {
    event.preventDefault();
    if(delay) return;
    delay = true;
    setTimeout(function(){delay = false},200)
    var wd = event.originalEvent.wheelDelta || -event.originalEvent.detail;
    var a= $('.IndexSection');
    if(wd < 0) {
     a.each(function(){
     var t = $(this).position()[0].top;
        if(t >= 40) return false;
});
    }
    else {
      for(var i = a.length-1 ; i >= 0 ; i--) {
        var t = a[i].getClientRects()[0].top;
        if(t < -20) break;
      }
    }
    $('html,body').animate({
      scrollTop: a.eq(i).offset().top
    });
  });
})();

对不起，伙计们，我真是个白痴，这是一个拼写错误，哈哈……没什么大不了的，现在工作得很好。。。

的打字错误

    var a= document.getElementsByClassName('.IndexSection');

我不需要在IndexSection类之前加一个点，所以我只需要用这个键入它

var a= document.getElementsByClassName('IndexSection');

所有的代码都经过编辑，现在运行良好。。thx适用于响应的用户

也许是这样的：

var lastScrollPos=0, scrollDirection='down', scrollMonitor=true;
$(function(){
	$(".skippage").click(function() {
	  $('html, body').animate({
		scrollTop: $("#content").offset().top
	  }, 300);
	});
	$(window).scroll(function(){
		currScrollPos = $(window).scrollTop();
		scrollDirection = (currScrollPos>lastScrollPos) ? 'down' : 'up';
		
		if (scrollDirection=='down' && scrollMonitor){
			scrollDelta = currScrollPos - lastScrollPos;
			if (scrollDelta > 40){
				scrollMonitor = false;
				$('html, body').animate({
					scrollTop: $("#content").offset().top
				}, 900, function(){
					scrollMonitor = true;
					lastScrollPos = currScrollPos;
				});
			}
		}else if (scrollDirection=='up' && scrollMonitor){
			scrollDelta = lastScrollPos - currScrollPos;
			if (scrollDelta > 40){
				scrollMonitor = false;
				$('html, body').animate({
					scrollTop: $("#welcome").offset().top
				}, 900, function(){
					scrollMonitor = true;
					lastScrollPos = currScrollPos;
				});
			}
		}
	}); //END window.scroll
}); //END document.ready

html,body {width:100%;height:100%;padding:0;margin:0;}
.IndexSection {font-size:6em;color:#ccc;width:100%;}
div#welcome {height:100vh;background:white;text-align:center;margin:0;position:relative;}
.welcometext {background-color:red;top:50%;left:50%;transform:translate(-50%, -50%);height:70%;width:80%;float:none;margin:0 auto;text-align:center;position:absolute;}
.skippage {font-size:12px;color:red;position:absolute;bottom:2%;left:50%;transform:translate(-50%, -2%);}
div.navigation {background:#9C0;font-size:12px;height:10%;}
div#content {height:100vh;background:yellow;}

<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
  <div id="welcome" class="IndexSection row">
    <div class=" welcometext">
      welcome
    </div>
    <a href="#" class="skippage">Go Down</a>
  </div>
  <div id="content" class="IndexSection">
    <div class="navigation">
      option
    </div>
    Content
  </div>

     Scroll to the next question
    return void
    
    function auto scroll next question Selector
 
         Don't scroll if last question of a page with explanation to show
        if auto scroll next var  blockpage Changing  scroll to explanation 
            'html bodyanimate 
                scrollTop question Selector next offsettop  35  scroll top offset
             scroll speed