


Building a Klondike Solitaire Game: Adding a Simple Image Preloader with Vanilla JavaScript
Oct 23, 2024 pm 07:44 PMCreating a smooth user experience is a key priority in web development, especially when your site relies on large visuals. While working on my new shiny Klondike Solitaire game, I needed to ensure that the card images loaded in a way that felt natural and didn’t leave users staring at a blank screen. So, I decided to add a simple image preloader that could also show users how much of the image had loaded, using nothing but vanilla JavaScript, HTML, and CSS. Here’s how I did it.
Step 1: Basic Setup
First things first, I created a simple file structure to keep things tidy. Here’s what it looked like:
klondike-preloader/ ├── index.html ├── styles.css └── script.js
This way, I had separate files for the HTML structure, the styling, and the JavaScript logic.
Step 2: Building the HTML Structure
In the HTML file, I set up a button to start the image loading process, a progress bar to show how far along the loading was, and a spot to display the image once it was ready.
index.html
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Klondike Solitaire Image Preloader</title> <link rel="stylesheet" href="styles.css"> </head> <body> <button id="load-button">Load Solitaire Image</button> <div id="progress-bar"> <div id="progress"></div> </div> <div id="image-container"> <img id="image" alt="Klondike Solitaire Card" /> </div> <script src="script.js"></script> </body> </html>
Step 3: Styling the Progress Bar and Layout
With the structure in place, I moved on to styling. I wanted the progress bar to stay hidden until the image actually started loading.
styles.css
#progress-bar { width: 100%; background: lightgray; margin-bottom: 10px; height: 20px; display: none; /* Hidden at first */ } #progress { width: 0%; height: 100%; background: green; } #image-container { display: none; /* Also hidden initially */ } #load-button { margin-bottom: 10px; padding: 10px 20px; font-size: 16px; cursor: pointer; }
Step 4: Adding JavaScript for Image Loading
Now for the JavaScript! Here’s what I did:
- Triggered Image Loading: Clicking the button starts loading the image.
- Updated the Progress Bar: Showed the bar and adjusted its width as the image loaded.
- Fallback for When Content Length Isn't Available: Used a default size to calculate progress in case the server didn’t provide the total size.
script.js
const progressBar = document.getElementById('progress'); const imageContainer = document.getElementById('image-container'); const imageElement = document.getElementById('image'); const loadButton = document.getElementById('load-button'); // Default fallback size in bytes const DEFAULT_SIZE_BYTES = 500 * 1024; // 500 KB function loadImage(url) { const xhr = new XMLHttpRequest(); xhr.open('GET', url, true); xhr.responseType = 'blob'; let totalSize = DEFAULT_SIZE_BYTES; document.getElementById('progress-bar').style.display = 'block'; xhr.onprogress = (event) => { if (event.lengthComputable) { totalSize = event.total; } const percentComplete = (event.loaded / totalSize) * 100; progressBar.style.width = percentComplete + '%'; }; xhr.onload = () => { if (xhr.status === 200) { const blob = xhr.response; const objectUrl = URL.createObjectURL(blob); imageElement.src = objectUrl; imageContainer.style.display = 'block'; progressBar.parentNode.style.display = 'none'; } }; xhr.onerror = () => { console.error('Image loading failed.'); }; xhr.send(); } loadButton.addEventListener('click', () => { loadImage('https://example.com/your-image.jpg'); });
Key Points:
- Used XMLHttpRequest to Fetch the Image: Tracked progress with onprogress and handled the image as a blob.
- Fallback for Default Size: Ensured the progress bar worked even if the server didn’t send the file size.
- Cleaned Up After Loading: Hid the progress bar and showed the loaded image.
Step 5: Testing
After coding, I tested it with different image sizes and adjusted the default size to make sure it provided a realistic loading experience. You can try the code on codepen: https://codepen.io/quantotius/pen/KKOXxqP
Conclusion
And there you have it! A basic, yet effective way to preload images and improve the user experience using vanilla JavaScript. Perfect for a game like Klondike Solitaire where visual feedback is a must. Try it out, and if you get stuck, feel free to ask for help!
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