How to Handle File Drag and Drop Uploads
How to build drag-and-drop file upload zones using HTML Drag and Drop APIs and modern fetch progress trackers.
Design the Visual Drop Zone
Create an upload area wrapper element in your UI, styling it with distinct active and inactive state border configurations.
Prevent Default Browser Responses
Attach 'onDragOver' and 'onDragEnter' handlers to your zone. Call 'event.preventDefault()' to stop the browser from opening the dropped file in a new tab.
Track Active Drag State Flags
Toggle a boolean state variable 'isDragging' to true on drag enter, and flip it back to false on drag leave to update visual styles.
Capture Dropped Data Files
Attach an 'onDrop' handler. Call 'event.preventDefault()' and extract the dropped files from the event object using 'event.dataTransfer.files'.
Validate File Size and Type
Loop through the captured file objects, checking 'file.type' against allowed formats and 'file.size' against maximum size limits before accepting them.
Append Items to FormData Instances
Instantiate a new 'FormData()' object container and append valid file objects to it using 'formData.append("file", file)'.
Dispatch Upload Network Operations
Send the 'FormData' object to your backend storage server using an async Axios or fetch post request, configuring headers to support 'multipart/form-data'.
Track Live Progress Percentages
Pass an 'onUploadProgress' callback configuration option to Axios to compute upload progress percentage calculations in real-time.
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