Edit in JSFiddle

var input = document.getElementById('files');
var output = document.getElementById('output');

input.onchange = function(e) {
  var files = e.target.files; // FileList
    for (var i = 0, f; f = files[i]; ++i){
        console.debug(files[i].webkitRelativePath);
        output.innerText  = output.innerText + files[i].webkitRelativePath+"\n";
    }
}
<input type="file" id="files" name="files[]" multiple webkitdirectory />
<div id="output"></div>