HTML Setup

<div class="upload-area">
    <input type="file" id="file-input" multiple accept="image/*" />
    <label for="file-input">Drag & Drop Images Here or Click to Select</label>
    </div>
    
    <div class="image-preview"></div>

CSS for Styling

body {
        font-family: Arial, sans-serif;
    }
    
    .upload-area {
        border: 2px dashed #ccc;
        padding: 20px;
        text-align: center;
        transition: background-color 0.3s;
    }
    
    .upload-area:hover {
        background-color: #f0f0f0;
    }
    
    .image-preview {
        display: grid;
        grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
        gap: 10px;
        margin-top: 20px;
    }
    
    .image-preview img {
        width: 100%;
        height: auto;
    }

JavaScript for Functionality

const fileInput = document.getElementById("file-input");
    const previewContainer = document.querySelector(".image-preview");

    fileInput.addEventListener("change", (event) => {
        previewContainer.innerHTML = ""; // Clear previous images
        const files = event.target.files;
        
        for (let i = 0; i < files.length; i++) {
            const file = files[i];
            const reader = new FileReader();
            reader.onload = function(e) {
                const imgElement = document.createElement("img");
                imgElement.src = e.target.result;
                previewContainer.appendChild(imgElement);
            };
            reader.readAsDataURL(file);
        }
    });

    // Drag and Drop Functionality (optional)
    const uploadArea = document.querySelector(".upload-area");

    uploadArea.addEventListener("dragover", (e) => {
        e.preventDefault();
        // Add any style to indicate hovering
    });

    uploadArea.addEventListener("drop", (e) => {
        e.preventDefault();
        const files = e.dataTransfer.files;
        fileInput.files = files;
        // Trigger change event to load images
        fileInput.dispatchEvent(new Event("change"));
    });

Performance Tips

• Limit the number of files users can select at once for better performance.
• Consider resizing images on the client-side before displaying them to save memory.
• Using readAsDataURL is great for previews, and it’s generally easy to handle.

Feel free to build upon this! It gives a basic idea of how you can get your multi-image upload feature going. Good luck with the project!