Validated Multi-File Dropzone With Queue
The general-purpose uploader: strict pick-time validation, a visible queue, real progress, and retry that only resends what failed.
Create a multi-file dropzone uploader. The 160px dashed dropzone highlights indigo on dragover; a visible "Browse files" button triggers a hidden native input retained for accessibility. Accept PDF, JPG, PNG up to 10MB each, 5 files total, validating at pick time with per-file rejection rows stating the exact reason; accepted files queue as rows with a 40px thumbnail, name truncated to 40 chars, human size, an XHR-driven determinate progress bar, and cancel while uploading. Upload at most 3 files concurrently, holding the rest as "Queued". On a failed request the row turns red with "Retry" that resends only that file via the same XHR path; 413 and 415 responses show the server reason with a remove button instead of retry. Completed rows turn green with a checkmark and expose the returned file key. Fire an onSubmit callback with the list of uploaded keys when every row reaches a terminal state.




