Save files to dropbox using the save file function

This was what i was trying to build but it doesn't work. I get the file value but when executing it! It open the the image.

<form>
<input type="text" id="file_id" value="https://dl.dropboxusercontent.com/s/deroi5nwm6u7gdf/advice.png"><br>
<input type="submit" value="Send!" onclick="send()">
</form>
<script>
send = function() {
var file_id = document.getElementById('file_id').value;
document.write('<a href="'+file_id+'" class="dropbox-saver">123</a>');
}
</script>