jQuery ajax single file upload

I know this question has been asked a lot, and I tried at least 10 different codes to run this without success.
I'm trying to upload a single file with jquery.ajax, but it doesn't work.
the code below always outputs : 'please choose a file' because the file's name is not set or something

html:

jquery:

$(function(){

  $(document).ready(function(){
    var files;

    $('input[type=file]').on('change', prepareUpload);
    function prepareUpload(event){
      files = event.target.files;
    };
    $(':button').click(function(){
        var formData = new FormData();
        $.each(files, function(key, value){

          formData.append(key, value);
        });
        alert(formData);
        $.ajax({
          url: 'check.php',  
          type: 'GET',
          data: formData,
          success: function(data){ $('#result').html(data); }, 
          cache: false,
          contentType: false,

          processData: false
        });
    });
  });
});

php:

if(isset($_GET['file'])){

    $filename = $_FILES['file']['name'];
    if(isset($filename) && !empty($filename)){
        echo 'sup my man?!';
    }else{
        echo 'please choose a file';
    }
}else{
    echo 'not set';
}

I don't know what the problem is, I know it's in the FormData object creation because the alert- good to go, doesn't work.

BTW it is really important for me that it would be written in jQuery.