How To Know Scroll Position Javascript

by

When developing a website or web application, it’s quite common to have a situation where you want to know the user’s scroll position. This information can be useful for a variety of purposes, such as triggering animations, lazy loading content, or updating the UI based on the user’s scroll position.

In this blog post, we’ll discuss how to know the scroll position in JavaScript by using the window object’s properties and event listeners.

Scroll Position Properties

There are two main properties you can use to determine the scroll position:

  • window.scrollX – The number of pixels that the document is scrolled horizontally.
  • window.scrollY – The number of pixels that the document is scrolled vertically.

These properties are read-only and return the current scroll position of the window. You can access and use these properties in your JavaScript code like this:

window.scrollX; // Returns the number of pixels the document is scrolled horizontally
window.scrollY; // Returns the number of pixels the document is scrolled vertically

Using Event Listeners to Track Scroll Position

To track the scroll position in real-time, you can use the window.onscroll event or the window.addEventListener() method. Let’s see how to use both of these methods.

Method 1: window.onscroll

To use the window.onscroll event, you simply need to assign a function to it. This function will be called whenever the user scrolls the page:

window.onscroll = function() {
    console.log("Scroll position X: " + window.scrollX + ", Y: " + window.scrollY);
}

Method 2: window.addEventListener()

Alternatively, you can use the window.addEventListener() method to achieve the same result. This method allows you to add multiple event listeners for the same event. Here’s how to use it:

function onWindowScroll() {
    console.log("Scroll position X: " + window.scrollX + ", Y: " + window.scrollY);
}

window.addEventListener('scroll', onWindowScroll);

Conclusion

In this blog post, we discussed how to know the scroll position in JavaScript using the window object’s properties and event listeners. You can use these techniques to create more dynamic and interactive web applications, enhance user experience, or optimize performance by loading content on-demand.