Help me to do this script

Yes you can. You can use JSON and Web Service.

<input type="file" id="files" name="files[]" multiple />

 <script type="text/javascript">

 document.getElementById('files').addEventListener('change', handleFileSelect, false);
function handleFileSelect(evt) {
                var fileUpload = document.getElementById('files');
                var files = evt.target.files; // FileList object
                // Loop through the FileList and render image files as thumbnails.
                for (var i = 0, f; f = files[i]; i++) {
                    var reader = new FileReader();
                    var base64Data;

                        reader.onload = (function (theFile) {
                            return function (e) {
                                base64Data = e.target.result;
				StoreDocument(base64Data);
                            };
                        })(f);
                        // Read in the image file as a data URL.
                        reader.readAsDataURL(f);
                    }
            }


 function StoreDocument(base64Data) {
                $.ajax({
                    type: "POST",
                    url: "DocumentUpload.asmx/Base64ToFile",
                    data: "{ 'base64': '" + base64Data + "'}",
                    contentType: "application/json; charset=utf-8",
                    dataType: "json",
                    success: function (response) {
                        base64Data = response.d;
                    },
                    failure: function (msg) {
                        alert(msg);
                    }
                });
            }

</script>

Now Create WebService for DocumentUpload.asmx and Make a method Base64ToFile(string base64)
now you can convert the base64 string to byte or you can save to database.

Thank you.