How synchronize the scroll of two divs with JavaScript

by Silvia Mazzetta Date: 11-08-2021 javascript

In case you have two divs of different sizes you may sometimes want to scroll both at the same time but at different speeds depending on their size. For example, you could have text in one and images in the other and want to scroll both at the same time. To achieve this, we will do it with the jQuery JavaScript library.

And no....jQuery is not dead.

To synchronize the scroll positions we can use .scrollTop() to know the position of the content with respect to the top of the page.

First, we place the page div with the main content and then the block div with the secondary content that will scroll with respect to the main one according to its position. This second div will have to have a fixed position with respect to the page. That is to say, that in its CSS it will have to contain the artribute "position: fixed".

<div id="mypage">
  <p class="mypageHeader">my page header</p>
  <p>Here we place our text</p>
  <p>more text...</p>
  <p> class="footerPage">footer page</p>

<div id="box">
  <div id="boxHeight">
    <p class="boxheader">box header</p>
    <p>Here we place our text</p>
    <p>more text</p>
    <p class="boxfooter">footer box</p>

Let's go now with the JavaScript code. In pageH we get the difference between the height of the page div and the height of the window to calculate the height of the non-visible content. In pagT we get the scroll position of the window minus the height that we have already advanced in the page div.

Finally we move the block div correspondingly with respect to the page div so that they move the same proportional distance based on their height.

$(window).scroll(function() {      
  var pagH = $('#mypage').height() - $(this).height();      
  var pagT = this.scrollY - $('#mypage').offset().top;      
  $('#box').scrollTop(pagT / pagH * ($('#boxHeight').height() - $(this).height()));  

The styles of the divs are as follows:

body {    
position: relative;    
margin: 0 auto;  
#mypage {    
width: 550px;  
#mypage p {    
text-align: justify;  
#box {    
background: #027EBA;    
display: block;    
width: 200px;    
height: 100%;    
position: fixed;    
right: 20px;    
overflow: hidden;  
.mypageHeader, .footerPage {    
display: block;    
width: 100%;    
margin: 0 auto;    
background: red;    
color: white;    
font-weight: bold;    
font-size: 16px;  
.boxheader, .boxfooter {    
display: block;    
width: 100%;    
margin: 0 auto;    
background: green;    
color: white;    
font-weight: bold;    
font-size: 16px;  

IMPORTANT: don't forget to add jQuery.

by Silvia Mazzetta Date: 11-08-2021 javascript hits : 8076  
Silvia Mazzetta

Silvia Mazzetta

Web Developer, Blogger, Creative Thinker, Social media enthusiast, Italian expat in Spain, mom of little 7 years old geek, founder of  @manoweb. A strong conceptual and creative thinker who has a keen interest in all things relate to the Internet. A technically savvy web developer, who has multiple  years of website design expertise behind her.  She turns conceptual ideas into highly creative visual digital products. 


Related Posts

How to use the endsWith method in JavaScript

In this short tutorial, we are going to see what the endsWith method, introduced in JavaScript ES6, is and how it is used with strings in JavaScript. The endsWith method is…

What are javascript symbols and how can they help you?

Symbols are a new primitive value introduced by ES6. Their purpose is to provide us unique identifiers. In this article, we tell you how they work, in which way they…

Callbacks in JavaScript

Callback functions are the same old JavaScript functions. They have no special syntax, as they are simply functions that are passed as an argument to another function. The function that receives…

How to create PDF with JavaScript and jsPDF

Creating dynamic PDF files directly in the browser is possible thanks to the jsPDF JavaScript library. In the last part of this article we have prepared a practical tutorial where I…

How to make your own custom cursor for your website

When I started browsing different and original websites to learn from them, one of the first things that caught my attention was that some of them had their own cursors,…

Node.js and npm: introductory tutorial

In this tutorial we will see how to install and use both Node.js and the npm package manager. In addition, we will also create a small sample application. If you…

How to connect to MySQL with Node.js

Let's see how you can connect to a MySQL database using Node.js, the popular JavaScript runtime environment. Before we start, it is important to note that you must have Node.js installed…

JavaScript Programming Styles: Best Practices

When programming with JavaScript there are certain conventions that you should apply, especially when working in a team environment. In fact, it is common to have meetings to discuss standards…

Difference between arrow and normal functions in JavaScript

In this tutorial we are going to see how arrow functions differ from normal JavaScript functions. We will also see when you should use one and when you should use…

JavaScript Arrow functions: What they are and how to use them

In this article we are going to see what they are and how to use JavaScript Arrow Functions, a new feature introduced with the ES6 standard (ECMAScript 6). What are Arrow…

How to insert an element into an array with JavaScript

In this brief tutorial you will learn how to insert one or more elements into an array with JavaScript. For this we will use the splice function. The splice function will not…

What is the difference between primitives types and objects in JavaScript?

In this short tutorial we are going to look at the differences between primitive types and objects in JavaScript. To start with, we're going to look at what primitive types…