second file downloads not first

I've got a problem when i'm dragging over my upload zone (drag n drop). For example, I have two files 1.csv, 2.csv and when i'm trying to upload this two files, only second uploads(2.csv). I want to upload just first and set permission to uploading only first file if two or more has chosen. Please help;(

    dropContainer.ondragover = dropContainer.ondragenter = function(evt) {
    evt.preventDefault();
};

dropContainer.ondrop = function(evt) {
    fileInput.files = evt.dataTransfer.files;

    evt.preventDefault();
};

via Yaroslav Andriychuk