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How Can I Get File Size, Image Width, and Height Before Uploading a File Using HTML5 and JavaScript?
How Can I Get File Size, Image Width, and Height Before Uploading a File Using HTML5 and JavaScript?
Nov 25, 2024 am 10:40 AM
Get File Size, Image Width, and Height Before Upload
Obtaining file size and image dimensions before uploading is essential for validating and managing submissions. Here's how to achieve this using HTML5 and JavaScript:
Using HTML5 File API
The File API provides a mechanism to access information about files selected by the user. This can be leveraged to retrieve file size, image height, and width. Consider the following example:
const browseInput = document.getElementById('browse');
const previewContainer = document.getElementById('preview');
const handleFileSelection = (event) => {
previewContainer.innerHTML = '';
const files = event.target.files;
if (!files || files.length === 0) {
alert('No files selected!');
return;
}
for (const file of files) {
// Check if the file is an image
if (!file.type.startsWith('image/')) {
previewContainer.insertAdjacentHTML('beforeend', `Unsupported format: ${file.name}<br>`);
continue;
}
// Create an image element to calculate width and height
const img = new Image();
img.onload = () => {
previewContainer.appendChild(img);
const fileInfo = `
<div>
${file.name}
${img.width} × ${img.height}
${file.type}
${Math.round(file.size / 1024)} KB
</div>
`;
previewContainer.insertAdjacentHTML('beforeend', fileInfo);
};
// Load the image and release the URL when done
img.src = URL.createObjectURL(file);
}
};
browseInput.addEventListener('change', handleFileSelection);
Further Possibilities
This approach allows you to get file size, image width, and height before uploading, enabling better control over accepted file types and dimensions. Additionally, you can use this information for validation and display purposes, such as providing a preview of the selected images before submission.
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