Detecting scroll direction

It can be detected by storing the previous scrollTop value and comparing the current scrollTop value with it.

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 {
      // upscroll code
   }
   lastScrollTop = st <= 0 ? 0 : st; // For Mobile or negative scrolling
}, false);

Simple way to catch all scroll events (touch and wheel)

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

Use this to find the scroll direction. This is only to find the direction of the Vertical Scroll. Supports all cross browsers.

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;
}

Example

You can try doing this.

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%; }

Initialize an oldValue Get the newValue by listening to the event Subtract the two Conclude from the result Update oldValue with the newValue

// Initialization

let oldValue = 0;

//Listening on the event

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;
});

This is an addition to what prateek has answered.There seems to be a glitch in the code in IE so i decided to modify it a bit nothing fancy(just another condition)

$('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;
});});

This simple code would work: Check the console for results.

let scroll_position = 0;
let scroll_direction;

window.addEventListener('scroll', function(e){
    scroll_direction = (document.body.getBoundingClientRect()).top > scroll_position ? 'up' : 'down';
    scroll_position = (document.body.getBoundingClientRect()).top;
    console.log(scroll_direction);
});

While the accepted answer works, it is worth noting that this will fire at a high rate. This can cause performance issues for computationally expensive operations.

The recommendation from MDN is to throttle the events. Below is a modification of their sample, enhanced to detect scroll direction.

Modified from: https://developer.mozilla.org/en-US/docs/Web/API/Document/scroll_event

// ## function declaration
function scrollEventThrottle(fn) {
  let last_known_scroll_position = 0;
  let ticking = false;
  window.addEventListener("scroll", function () {
    let previous_known_scroll_position = last_known_scroll_position;
    last_known_scroll_position = window.scrollY;
    if (!ticking) {
      window.requestAnimationFrame(function () {
        fn(last_known_scroll_position, previous_known_scroll_position);
        ticking = false;
      });
      ticking = true;
    }
  });
}

// ## function invocation
scrollEventThrottle((scrollPos, previousScrollPos) => {
    if (previousScrollPos > scrollPos) {
      console.log("going up");
    } else {
      console.log("going down");
    }
});

You can get the scrollbar position using document.documentElement.scrollTop. And then it is simply matter of comparing it to the previous position.

I personally use this code to detect scroll direction in javascript... Just you have to define a variable to store lastscrollvalue and then use this if&else

let lastscrollvalue;

function headeronscroll() {

    // document on which scroll event will occur
    var a = document.querySelector('.refcontainer'); 

    if (lastscrollvalue == undefined) {

        lastscrollvalue = a.scrollTop;

        // sets lastscrollvalue
    } else if (a.scrollTop > lastscrollvalue) {

        // downscroll rules will be here
        lastscrollvalue = a.scrollTop;

    } else if (a.scrollTop < lastscrollvalue) {

        // upscroll rules will be here
        lastscrollvalue = a.scrollTop;

    }
}

If anyone looking to achieve it with React hooks

  const [scrollStatus, setScrollStatus] = useState({
    scrollDirection: null,
    scrollPos: 0,
  });

  useEffect(() => {
    window.addEventListener("scroll", handleScrollDocument);

    return () => window.removeEventListener("scroll", handleScrollDocument);
  }, []);

  function handleScrollDocument() {
    setScrollStatus((prev) => { // to get 'previous' value of state
      return {
        scrollDirection:
          document.body.getBoundingClientRect().top > prev.scrollPos
            ? "up"
            : "down",
        scrollPos: document.body.getBoundingClientRect().top,
      };
    });
  }

  console.log(scrollStatus.scrollDirection)

Modifying Prateek's answer, if there is no change in lastScrollTop, then it would be a horizontal scroll (with overflow in the x direction, can be used by using horizontal scrollbars with a mouse or using scrollwheel + shift.

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
});

This seems to be working fine.

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');
        }



    });
});