Browser Specific issue - One input file field data

Question

function assignFile(obj){
     var file2 = document.querySelector('#fileData');
     file2.files = obj.files;
     console.log(file2.files);
}

   
<form action="" method="post" enctype="multipart/form-data">
    <input type="file" name="fileData[]" id="fileData" multiple="" style="display: none;" />
    File: <input type="file" id="file" name="file" onchange="assignFile(this)" />
    <input type="submit" name="submit" value="Submit" />
</form>

I have two file fields. I want to assign file data to fileData field. I have posted my code. This code working fine in chrome. But not working in mozilla. Could you please check.