Dropzone: prevent addfile twice

Question

I'm using dropzone to upload images to gallery. I'm submiting by button. Is it possible to prevent adding same file twice? I'm not really sure if checking name or name and size. Here's my code:

<script>
      var i = 0;
      Dropzone.options.myDropzone = {
        init: function() {
            this.on("addedfile", function(file) {
            i=++i;

check filenames and filesizes of other files here

----------->if(){
                myDropzone.removeFile(file);
            }


            var inputs = Dropzone.createElement('<div class="dz-image-metadata"><label for="'+i+'_title">Nazov</label><input type="hidden" name="'+i+'_filename" value="'+file.name+'"><input type="text" name="'+i+'_title" value="'+file.name+'" /><label for="">Popis</label><input type="text" name="'+i+'_desc"></div>');
            file.previewElement.appendChild(inputs);
            var removeButton = Dropzone.createElement("<button class=\"dz-button\">Vymazať</button>");
            var _this = this;
            removeButton.addEventListener("click", function(e) {
              e.preventDefault();
              e.stopPropagation();
              i=--i;
              _this.removeFile(file);
            });
            file.previewElement.appendChild(removeButton);
          });
          var myDropzone = this;
           $("#submit-all").click(function (e) {
            e.preventDefault();
            e.stopPropagation();
            myDropzone.processQueue();
            i=0;
        }
        );

         this.on("successmultiple", function(files, response) {
           console.log(response);
        });

         this.on("complete", function(file) {
            myDropzone.removeFile(file);
        });

        this.on("errormultiple", function(files, response) {
             });
        },
        autoProcessQueue: false,
        previewsContainer: ".dropzone",
        uploadMultiple: true,
        parallelUploads: 25,
        maxFiles: 25,
      };
    </script>

Answer 1

Checking the file name and size should be fine. I already tested that and it had worked almost fine for me and haven't crossed any issues with it.

The original thread I landed in was a Git issue #639 where a community member posted his solution for name and size verification.

That trick was also mentioned in a similar post answer.

Answer 2

 this.on("addedfile", function (file) {
                    if (this.files.length) {
                        var i, len, pre;
                        for (i = 0, len = this.files.length; i < len - 1; i++) {
                            if (this.files[i].name == file.name) {
                                alert("The Doc.: " + file.name + " is already registered.")
                                return (pre = file.previewElement) != null ? pre.parentNode.removeChild(file.previewElement) : void 0;
                            }
                        }
                    }
                });

Answer 3

Add these simple lines of code:

myDropzone.on("addedfile", function(file) {
    if (this.files.length) {
        var _i, _len;
        for (_i = 0, _len = this.files.length; _i < _len - 1; _i++) // -1 to exclude current file
        {
            if(this.files[_i].name === file.name && this.files[_i].size === file.size && this.files[_i].lastModified.toString() === file.lastModified.toString())
            {
                this.removeFile(file);
            }
        }
    }
});