Finding out the exact number of pixels a user will scroll when using the mouse wheel in Javascript

Question

Finding out the exact number of pixels a user will scroll when using the mouse wheel in Javascript

Is there a way to calculate the number of pixels that will be moved by the vertical scroll bar when a user scrolls using the mouse wheel in JavaScript?

In my situation, the user's scrolling will result in an offsetTop change between 200px to 1000px, and I would like to know this in advance. Is there any method to determine this using JavaScript?

javascript html css reactjs angular

Answer 1

Answer №1

If I grasp the essence of your inquiry correctly, the simple response is 'no'. To clarify this point, let's consider an analogous scenario:

Suppose I detect a keydown event on the down arrow. Can I accurately predict when the user will release the down key?

This feat is unattainable. The timing of key releases hinges solely on the user's discretion and cannot be forecasted.

When it comes to mouse wheel events specifically, one must also take into account variations in hardware/mouse and software/browser configurations, further complicating an already daunting task.

A different strategy: Implement debouncing for mouse-wheel events

Lacking more context about your overarching goal makes it challenging to ascertain if this technique will prove beneficial. However, employing a debounce function can standardize the occurrence of mouse-wheel events over a designated timeframe. Consequently, regardless of whether the user scrolls for 0.5 seconds or 1 second, only one event will register, streamlining any necessary computations.

Here is a rudimentary example using Javascript on Stackblitz, showcasing the debouncing of a mouse-wheel event every 0.1 seconds. In the case of continuous mouse-wheel scrolling, only the initial event should trigger.

RxJS features a built-in debounceTime function. While my familiarity with React is limited, the application of this function to mouse events would likely adhere to the same fundamental principle demonstrated in the earlier example.

Answer 2

If I grasp the essence of your inquiry correctly, the simple response is 'no'. To clarify this point, let's consider an analogous scenario:

Suppose I detect a keydown event on the down arrow. Can I accurately predict when the user will release the down key?

This feat is unattainable. The timing of key releases hinges solely on the user's discretion and cannot be forecasted.

When it comes to mouse wheel events specifically, one must also take into account variations in hardware/mouse and software/browser configurations, further complicating an already daunting task.

A different strategy: Implement debouncing for mouse-wheel events

Lacking more context about your overarching goal makes it challenging to ascertain if this technique will prove beneficial. However, employing a debounce function can standardize the occurrence of mouse-wheel events over a designated timeframe. Consequently, regardless of whether the user scrolls for 0.5 seconds or 1 second, only one event will register, streamlining any necessary computations.

Here is a rudimentary example using Javascript on Stackblitz, showcasing the debouncing of a mouse-wheel event every 0.1 seconds. In the case of continuous mouse-wheel scrolling, only the initial event should trigger.

RxJS features a built-in debounceTime function. While my familiarity with React is limited, the application of this function to mouse events would likely adhere to the same fundamental principle demonstrated in the earlier example.

Answer 3

Answer №2

Hello @Dip Parmar, I have provided you with the implementation of tracking both the previous scroll position and the current scroll position in a separate file named useDocumentScroll.js. The previous scroll position is considered as the end point of one scroll operation that you are interested in. This code snippet is written using React functional hooks. You can integrate this functionality into RequiredPage.js by customizing it according to your needs. Additionally, two variables - isScrolledDown and isMinimumScrolled, have been included for your reference, although their specific usage is not mentioned. Kindly find the code below:

File: useDocumentScroll.js

import { useEffect, useState } from "react";

function useDocumentScroll(callback) {
  const [, setScrollPosition] = useState(0);
  let previousScrollTop = 0;

  function handleDocumentScroll() {
    const { scrollTop: currentScrollTop } =
      document.documentElement || document.body;

    setScrollPosition(previousPosition => {
      previousScrollTop = previousPosition;
      return currentScrollTop;
    });

    callback({ previousScrollTop, currentScrollTop });
  }

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

    return () =>
      window.removeEventListener("scroll", handleDocumentScroll); // eslint-disable-next-line
  }, []);
}

export default useDocumentScroll;

File: RequiredPage.js

import React from "react";    
import useDocumentScroll from "./useDocumentScroll";

export default function RequiredPage() {
const MINIMUM_SCROLL = 80;

useDocumentScroll(callbackData => {
const { previousScrollTop, currentScrollTop } = callbackData;
const isScrolledDown = previousScrollTop < currentScrollTop;
const isMinimumScrolled = currentScrollTop > MINIMUM_SCROLL;
});

return (
     <div>
     <h1>Some Text or Add some Lorem Ipsum </h1>
     </div>
       );
    }

Answer 4

Hello @Dip Parmar, I have provided you with the implementation of tracking both the previous scroll position and the current scroll position in a separate file named useDocumentScroll.js. The previous scroll position is considered as the end point of one scroll operation that you are interested in. This code snippet is written using React functional hooks. You can integrate this functionality into RequiredPage.js by customizing it according to your needs. Additionally, two variables - isScrolledDown and isMinimumScrolled, have been included for your reference, although their specific usage is not mentioned. Kindly find the code below:

File: useDocumentScroll.js

import { useEffect, useState } from "react";

function useDocumentScroll(callback) {
  const [, setScrollPosition] = useState(0);
  let previousScrollTop = 0;

  function handleDocumentScroll() {
    const { scrollTop: currentScrollTop } =
      document.documentElement || document.body;

    setScrollPosition(previousPosition => {
      previousScrollTop = previousPosition;
      return currentScrollTop;
    });

    callback({ previousScrollTop, currentScrollTop });
  }

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

    return () =>
      window.removeEventListener("scroll", handleDocumentScroll); // eslint-disable-next-line
  }, []);
}

export default useDocumentScroll;

File: RequiredPage.js

import React from "react";    
import useDocumentScroll from "./useDocumentScroll";

export default function RequiredPage() {
const MINIMUM_SCROLL = 80;

useDocumentScroll(callbackData => {
const { previousScrollTop, currentScrollTop } = callbackData;
const isScrolledDown = previousScrollTop < currentScrollTop;
const isMinimumScrolled = currentScrollTop > MINIMUM_SCROLL;
});

return (
     <div>
     <h1>Some Text or Add some Lorem Ipsum </h1>
     </div>
       );
    }

Answer 5

Answer №3

I grasped your desire to determine the amount of pixels that will be scrolled when a scroll event commences.

However, this is not solely a web or code issue. The scrolling action continues until the user decides to halt it.

This process is also influenced by the mouse wheel hardware. Different mice have varying wheels - some stop immediately upon releasing the finger, while others with softer gears allow for continued motion (in accordance with Newton's Law of Motion).

Web developers do not have control over future hardware performances such as predicting when a user will release a key or mouse button.

The only data available to us pertains to the hardware's current or completed actions like keyup, keydown, click, and scrolling.

These events provide insight into present activity and what occurred just before.

The only way to anticipate the duration of a scroll is through Machine Learning, by analyzing user scrolling patterns and understanding their scrolling device.

But why is this needed? One potential use case is developing a ML model to comprehend user scrolling behavior.

In a scenario where a user's scroll results in an offsetTop change between 200px to 1000px, can we predict this using JavaScript?

For this specific case, there is no necessity to obtain the scrolling pixels before halting. A basic scroll event is sufficient.

You might want to incorporate a small animation before reaching 1000px, which can be achieved directly through CSS and JavaScript by creating an event listener on scroll (e.g., if current offsetTop == 1000px then...)

This snippet informs you about the number of pixels scrolled during a scroll event (completed task).

const pageHeight=document.documentElement.scrollHeight;
console.log(pageHeight)
document.querySelector('.rem').innerHTML="You have scrolled "+window.pageYOffset+". Scroll ends after "+((pageHeight-window.innerHeight)-window.pageYOffset);
document.onscroll = () =>{
if(window.pageYOffset>1000){
 var cl=document.getElementById("gm");
 cl.classList.add("wow");
}
if(window.pageYOffset<1000){
 var cl=document.getElementById("gm");
 cl.classList.remove("wow");
}
document.querySelector('.rem').innerHTML="You have scrolled "+window.pageYOffset+". Scroll ends after "+((pageHeight-window.innerHeight)-window.pageYOffset);
};

.rem{
position:fixed;
top:0;
}
.demo{
height:5000px;
}

.wow{
background:#FFCB2B;
transition:2s;
}

<span class="rem" id="xy"></span>
<div class="demo" id="gm">
<div>

Indeed, I will create a simple machine learning JS script for tracking scroll events by studying user behavior.

Currently, I am focusing on training for unidirectional scrolling. Each scroll will either be upscroll or downscroll.

The first 10 scrolls will be dedicated to learning. Afterward, the script predicts upcoming scroll values based on the learned data.

The model continuously learns and improves, providing more realistic predictions with higher learning values.

const pageHeight=document.documentElement.scrollHeight;
const scrollPoints=[];
var prevScroll=0;
var currentScroll=0;
learnValue=0;
var scrollTimer = -1;
console.log(pageHeight)
document.querySelector('.rem').innerHTML="You have scrolled "+window.pageYOffset+". Scroll ends after "+((pageHeight-window.innerHeight)-window.pageYOffset);

document.onscroll = () =>{

if (scrollTimer != -1)
       clearTimeout(scrollTimer);
  scrollTimer = window.setTimeout("scrollFinished()", 300);
if(learnValue>=10){
var calculatedAvg=averageScroll()
document.querySelector('.rem').innerHTML="Your expected scroll pixels are "+calculatedAvg;
}

};
function averageScroll(){
  let currentAvg=0
scrollPoints.forEach((item, index)=>{
      if(index!=0)
        currentAvg=(currentAvg+item)/(2)
       else
          currentAvg=item
});
return currentAvg;
}
function scrollFinished() {
        learnValue=learnValue+1;
        curPoint=window.pageYOffset
        currentScroll=Math.abs(window.pageYOffset-prevScroll);
        prevScroll=curPoint;
        scrollPoints[learnValue]=currentScroll
        console.log("Current Scroll was "+ currentScroll)
        if(learnValue<=10)
        document.querySelector('.rem').innerHTML="Current Scrolled pixels were "+currentScroll+" learning "+ learnValue + " of 10";
        
    }

.rem{
position:fixed;
top:0;
}
.demo{
height:50000px;
}

<span class="rem" id="xy"></span>
<div class="demo">
<div>

Answer 6

I grasped your desire to determine the amount of pixels that will be scrolled when a scroll event commences.

However, this is not solely a web or code issue. The scrolling action continues until the user decides to halt it.

This process is also influenced by the mouse wheel hardware. Different mice have varying wheels - some stop immediately upon releasing the finger, while others with softer gears allow for continued motion (in accordance with Newton's Law of Motion).

Web developers do not have control over future hardware performances such as predicting when a user will release a key or mouse button.

The only data available to us pertains to the hardware's current or completed actions like keyup, keydown, click, and scrolling.

These events provide insight into present activity and what occurred just before.

The only way to anticipate the duration of a scroll is through Machine Learning, by analyzing user scrolling patterns and understanding their scrolling device.

But why is this needed? One potential use case is developing a ML model to comprehend user scrolling behavior.

In a scenario where a user's scroll results in an offsetTop change between 200px to 1000px, can we predict this using JavaScript?

For this specific case, there is no necessity to obtain the scrolling pixels before halting. A basic scroll event is sufficient.

You might want to incorporate a small animation before reaching 1000px, which can be achieved directly through CSS and JavaScript by creating an event listener on scroll (e.g., if current offsetTop == 1000px then...)

This snippet informs you about the number of pixels scrolled during a scroll event (completed task).

const pageHeight=document.documentElement.scrollHeight;
console.log(pageHeight)
document.querySelector('.rem').innerHTML="You have scrolled "+window.pageYOffset+". Scroll ends after "+((pageHeight-window.innerHeight)-window.pageYOffset);
document.onscroll = () =>{
if(window.pageYOffset>1000){
 var cl=document.getElementById("gm");
 cl.classList.add("wow");
}
if(window.pageYOffset<1000){
 var cl=document.getElementById("gm");
 cl.classList.remove("wow");
}
document.querySelector('.rem').innerHTML="You have scrolled "+window.pageYOffset+". Scroll ends after "+((pageHeight-window.innerHeight)-window.pageYOffset);
};

.rem{
position:fixed;
top:0;
}
.demo{
height:5000px;
}

.wow{
background:#FFCB2B;
transition:2s;
}

<span class="rem" id="xy"></span>
<div class="demo" id="gm">
<div>

Indeed, I will create a simple machine learning JS script for tracking scroll events by studying user behavior.

Currently, I am focusing on training for unidirectional scrolling. Each scroll will either be upscroll or downscroll.

The first 10 scrolls will be dedicated to learning. Afterward, the script predicts upcoming scroll values based on the learned data.

The model continuously learns and improves, providing more realistic predictions with higher learning values.

const pageHeight=document.documentElement.scrollHeight;
const scrollPoints=[];
var prevScroll=0;
var currentScroll=0;
learnValue=0;
var scrollTimer = -1;
console.log(pageHeight)
document.querySelector('.rem').innerHTML="You have scrolled "+window.pageYOffset+". Scroll ends after "+((pageHeight-window.innerHeight)-window.pageYOffset);

document.onscroll = () =>{

if (scrollTimer != -1)
       clearTimeout(scrollTimer);
  scrollTimer = window.setTimeout("scrollFinished()", 300);
if(learnValue>=10){
var calculatedAvg=averageScroll()
document.querySelector('.rem').innerHTML="Your expected scroll pixels are "+calculatedAvg;
}

};
function averageScroll(){
  let currentAvg=0
scrollPoints.forEach((item, index)=>{
      if(index!=0)
        currentAvg=(currentAvg+item)/(2)
       else
          currentAvg=item
});
return currentAvg;
}
function scrollFinished() {
        learnValue=learnValue+1;
        curPoint=window.pageYOffset
        currentScroll=Math.abs(window.pageYOffset-prevScroll);
        prevScroll=curPoint;
        scrollPoints[learnValue]=currentScroll
        console.log("Current Scroll was "+ currentScroll)
        if(learnValue<=10)
        document.querySelector('.rem').innerHTML="Current Scrolled pixels were "+currentScroll+" learning "+ learnValue + " of 10";
        
    }

.rem{
position:fixed;
top:0;
}
.demo{
height:50000px;
}

<span class="rem" id="xy"></span>
<div class="demo">
<div>

Answer 7

Answer №4

Your feedback about fixing the footer within an iframe while adjusting its position based on the parent window scroll has been noted. I have created a solution that aligns with your requirements:

For a better view, check it out in fullscreen mode

var block=document.getElementById('div');
    
window.addEventListener('scroll',function(){
var scrolled=window.scrollY;
   
if(scrolled>=471 && scrolled<=963){
    block.style.overflowY="scroll";
    
    
    if(block.scrollTop>=519){
        block.style.overflowY="hidden";
    
    }
    else if(block.scrollTop>=0){
        
    block.scrollTop+=(scrolled-519);
    window.scrollTo(0,scrolled);
    
}


}
else{
    if(scrolled<=741){
    block.style.overflowY="scroll";
   
    block.scrollTop=0;
    if(block.scrollTop<=0){
        block.style.overflowY="hidden";
    }
}

    window.scrollTo(0,scrolled);
}
});

*{
            margin: 0px;
            padding:0px;
        
        }
        body{
            height:2400px;
        }
        p{
            font-size: 20px;
        }
        #div{
           position: absolute;
           scroll-behavior: smooth;
           height:401px; 
           width: 97vw;
           margin-top:570px;
           background-color:black;
           color: white; 
           padding:10px;
           z-index: 14;
        }
        #div::-webkit-scrollbar {
  display: none;
}
        #p_3{
            position: absolute;
            margin-top:940px;
            background-color: white;
            color: black;
            z-index: 11;
            width: 100vw;
            padding: 10px;
            
        }
        #p_1{
            position: absolute;
            background-color: white;
            color: black;
            z-index: 11;
            width: 100vw;
            padding: 10px;
            
        }

<div id="p_1">
// Lorem Ipsum content goes here
</div>
<div id="div">
    <div id="p">
    // More Lorem Ipsum content for demonstration
</div>
<br>
<br>
<br>
<div id="p_3">
// Further Lorem Ipsum content
</div>

If you prefer using mouseWheel, consider implementing IntersectionObserver.

The “Intersection Observer” allows you to track changes in element overlap asynchronously, in relation to other elements or the viewport.

Answer 8

Your feedback about fixing the footer within an iframe while adjusting its position based on the parent window scroll has been noted. I have created a solution that aligns with your requirements:

For a better view, check it out in fullscreen mode

var block=document.getElementById('div');
    
window.addEventListener('scroll',function(){
var scrolled=window.scrollY;
   
if(scrolled>=471 && scrolled<=963){
    block.style.overflowY="scroll";
    
    
    if(block.scrollTop>=519){
        block.style.overflowY="hidden";
    
    }
    else if(block.scrollTop>=0){
        
    block.scrollTop+=(scrolled-519);
    window.scrollTo(0,scrolled);
    
}


}
else{
    if(scrolled<=741){
    block.style.overflowY="scroll";
   
    block.scrollTop=0;
    if(block.scrollTop<=0){
        block.style.overflowY="hidden";
    }
}

    window.scrollTo(0,scrolled);
}
});

*{
            margin: 0px;
            padding:0px;
        
        }
        body{
            height:2400px;
        }
        p{
            font-size: 20px;
        }
        #div{
           position: absolute;
           scroll-behavior: smooth;
           height:401px; 
           width: 97vw;
           margin-top:570px;
           background-color:black;
           color: white; 
           padding:10px;
           z-index: 14;
        }
        #div::-webkit-scrollbar {
  display: none;
}
        #p_3{
            position: absolute;
            margin-top:940px;
            background-color: white;
            color: black;
            z-index: 11;
            width: 100vw;
            padding: 10px;
            
        }
        #p_1{
            position: absolute;
            background-color: white;
            color: black;
            z-index: 11;
            width: 100vw;
            padding: 10px;
            
        }

<div id="p_1">
// Lorem Ipsum content goes here
</div>
<div id="div">
    <div id="p">
    // More Lorem Ipsum content for demonstration
</div>
<br>
<br>
<br>
<div id="p_3">
// Further Lorem Ipsum content
</div>

If you prefer using mouseWheel, consider implementing IntersectionObserver.

The “Intersection Observer” allows you to track changes in element overlap asynchronously, in relation to other elements or the viewport.

Answer 9

Answer №5

It seems like you are looking for a solution that involves handling scroll events in JavaScript. Here is an example code snippet:

window.addEventListener("scroll", (event) => {
    let scroll = this.scrollY;
    console.log(scroll)
});

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8>
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body style="height:900px;background-color:limegreen;">
  
</body>
</html>

Answer 10

It seems like you are looking for a solution that involves handling scroll events in JavaScript. Here is an example code snippet:

window.addEventListener("scroll", (event) => {
    let scroll = this.scrollY;
    console.log(scroll)
});

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8>
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body style="height:900px;background-color:limegreen;">
  
</body>
</html>

Finding out the exact number of pixels a user will scroll when using the mouse wheel in Javascript

Answer №1

Answer №2

Answer №3

However, this is not solely a web or code issue. The scrolling action continues until the user decides to halt it.

Answer №4

For a better view, check it out in fullscreen mode

If you prefer using mouseWheel, consider implementing IntersectionObserver.

The “Intersection Observer” allows you to track changes in element overlap asynchronously, in relation to other elements or the viewport.

Answer №5

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