所以我试图使用JavaScript滚动调用一个函数。但是我想知道我是否可以不使用jQuery检测滚动的方向。如果没有,有什么变通办法吗?

我想只放一个“顶部”按钮,但如果可以的话,我想避免这个按钮。

我现在刚刚尝试使用这段代码,但它不起作用:

if document.body.scrollTop <= 0 {
    alert ("scrolling down")
} else {
    alert ("scrolling up")
}

当前回答

可以通过存储之前的scrollTop值并将当前scrollTop值与其进行比较来检测它。

JavaScript:

var lastScrollTop = 0;

// element should be replaced with the actual target element on which you have applied scroll, use window in case of no target element.
element.addEventListener("scroll", function(){ // or window.addEventListener("scroll"....
   var st = window.pageYOffset || document.documentElement.scrollTop; // Credits: "https://github.com/qeremy/so/blob/master/so.dom.js#L426"
   if (st > lastScrollTop) {
      // downscroll code
   } else if (st < lastScrollTop) {
      // upscroll code
   } // else was horizontal scroll
   lastScrollTop = st <= 0 ? 0 : st; // For Mobile or negative scrolling
}, false);

其他回答

初始化一个oldValue 通过监听事件获取newValue 两者相减 从结果得出结论 用newValue更新oldValue

/ /初始化

let oldValue = 0;

//监听事件

window.addEventListener('scroll', function(e){

    // Get the new Value
    newValue = window.pageYOffset;

    //Subtract the two and conclude
    if(oldValue - newValue < 0){
        console.log("Up");
    } else if(oldValue - newValue > 0){
        console.log("Down");
    }

    // Update the old value
    oldValue = newValue;
});

使用这个来找到滚动方向。这只是为了找到垂直滚动的方向。支持所有跨浏览器。

var scrollableElement = document.body; //document.getElementById('scrollableElement');

scrollableElement.addEventListener('wheel', checkScrollDirection);

function checkScrollDirection(event) {
  if (checkScrollDirectionIsUp(event)) {
    console.log('UP');
  } else {
    console.log('Down');
  }
}

function checkScrollDirectionIsUp(event) {
  if (event.wheelDelta) {
    return event.wheelDelta > 0;
  }
  return event.deltaY < 0;
}

例子

这是对prateek的回答的补充。在IE的代码中似乎有一个小故障,所以我决定修改它一点也不花哨(只是另一个条件)

$('document').ready(function() {
var lastScrollTop = 0;
$(window).scroll(function(event){
   var st = $(this).scrollTop();
   if (st > lastScrollTop){
       console.log("down")
   }
   else if(st == lastScrollTop)
   {
     //do nothing 
     //In IE this is an important condition because there seems to be some instances where the last scrollTop is equal to the new one
   }
   else {
      console.log("up")
   }
   lastScrollTop = st;
});});

你可以试试这样做。

function scrollDetect(){ var lastScroll = 0; window.onscroll = function() { let currentScroll = document.documentElement.scrollTop || document.body.scrollTop; // Get Current Scroll Value if (currentScroll > 0 && lastScroll <= currentScroll){ lastScroll = currentScroll; document.getElementById("scrollLoc").innerHTML = "Scrolling DOWN"; }else{ lastScroll = currentScroll; document.getElementById("scrollLoc").innerHTML = "Scrolling UP"; } }; } scrollDetect(); html,body{ height:100%; width:100%; margin:0; padding:0; } .cont{ height:100%; width:100%; } .item{ margin:0; padding:0; height:100%; width:100%; background: #ffad33; } .red{ background: red; } p{ position:fixed; font-size:25px; top:5%; left:5%; } <div class="cont"> <div class="item"></div> <div class="item red"></div> <p id="scrollLoc">0</p> </div>

捕捉所有滚动事件(触摸和滚轮)的简单方法

window.onscroll = function(e) {
  // print "false" if direction is down and "true" if up
  console.log(this.oldScroll > this.scrollY);
  this.oldScroll = this.scrollY;
}