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

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;
});});

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

修改Prateek的答案,如果lastScrollTop没有变化,那么它将是一个水平滚动(在x方向溢出,可以使用鼠标使用水平滚动条或使用滚动轮+ shift来使用。

const containerElm = document.getElementById("container");

let lastScrollTop = containerElm.scrollTop;

containerElm.addEventListener("scroll", (evt) => {
  const st = containerElm.scrollTop;

  if (st > lastScrollTop) {
    console.log("down scroll");
  } else if (st < lastScrollTop) {
    console.log("up scroll");
  } else {
    console.log("horizontal scroll");
  }

  lastScrollTop = Math.max(st, 0); // For mobile or negative scrolling
});

这似乎工作得很好。

document.addEventListener('DOMContentLoaded', () => {

    var scrollDirectionDown;
    scrollDirectionDown = true;

    window.addEventListener('scroll', () => {

        if (this.oldScroll > this.scrollY) {
            scrollDirectionDown = false;
        } else {
            scrollDirectionDown = true;
        }
        this.oldScroll = this.scrollY;


        // test
        if (scrollDirectionDown) {
            console.log('scrolling down');
        } else {
            console.log('scrolling up');
        }



    });
});

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);