Duplicate Files

Prevent duplicate file names from being added to the queue using the onSelect callback to track added file names.

Drag & drop files here (no duplicates)

<div id="myUploader" class="mu-uploader">...</div>

var addedNames = {};
var uploader = new MultipleUpload(document.getElementById('myUploader'), {
 uploadUrl: '/api/upload',
 onSelect: function(file) {
 if (addedNames[file.name]) {
 showError(file.name + ' has already been added.');
 return false;
 }
 addedNames[file.name] = true;
 return true;
 },
 onQueueRemove: function(file) {
 delete addedNames[file.name];
 }
});

Catching the same file twice

preventDuplicates compares name and size against both the current queue and files already completed in this session. It catches the ordinary accident — selecting a folder, then selecting it again because the first attempt did not look like it worked.

What that comparison misses

The same image saved under two names is not a duplicate by this test, and two unrelated files that happen to share a name and size are. For real content identity you need a hash: computeHash with SHA-256, and dedupe on the server against its own copies.