How to Create a Lazy Image Loading Reveal with Vanilla JavaScript

📝 Description:

In this mini project, you’ll learn how to implement lazy image loading using pure JavaScript — no external libraries or frameworks required.

Instead of loading all images at once, this script delays the full-resolution image load until it’s ready, and then smoothly fades it in while removing a low-quality preview placeholder.

✨ What you'll learn:
1. Lazy loading logic using data-src
2. Preloading images with new Image()
3. Smooth transitions with onload and setTimeout
4. DOM manipulation to swap image sources and remove previews

This is a perfect lightweight solution for improving your website’s performance and user experience.

🔖 Tags (Hashtags):
#javascript #lazyloading #webperformance #frontend #webdevelopment #vanillajs #html #css #dommanipulation #lazyload #images #programmingtutorial

🚫 Warning:
Error: const wrapper = img.classest('img-wrapper');
Should be: const wrapper = img.closest('.img-wrapper');

🔗 Source code:
https://keepsnip.com/source/how-to-create-a-lazy-image-loading-reveal-with-vanilla-javascript

🖼️ Image source:

Visit unsplash.com

img 1: https://images.unsplash.com/photo-1748701821466-0b9f8bf839ac?q=80&w=1451&auto=format&fit=crop&ixlib=rb-4.1.0&ixid=M3wxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8fA%3D%3D

img 2: https://images.unsplash.com/photo-1596833504535-ca1a5a4b5c57?w=500&auto=format&fit=crop&q=60&ixlib=rb-4.1.0&ixid=M3wxMjA3fDB8MHxwaG90by1yZWxhdGVkfDF8fHxlbnwwfHx8fHw%3D

img 3: https://images.unsplash.com/photo-1621825347931-41fe02769c29?w=500&auto=format&fit=crop&q=60&ixlib=rb-4.1.0&ixid=M3wxMjA3fDB8MHxwaG90by1yZWxhdGVkfDV8fHxlbnwwfHx8fHw%3D

img 4: https://images.unsplash.com/photo-1593194634277-ba2834f5dcbb?w=500&auto=format&fit=crop&q=60&ixlib=rb-4.1.0&ixid=M3wxMjA3fDB8MHxwaG90by1yZWxhdGVkfDZ8fHxlbnwwfHx8fHw%3D

img 5: https://images.unsplash.com/photo-1642046268189-c53f2903b9c9?w=500&auto=format&fit=crop&q=60&ixlib=rb-4.1.0&ixid=M3wxMjA3fDB8MHxwaG90by1yZWxhdGVkfDE1fHx8ZW58MHx8fHx8