function getRedditFeed() {
  var topic = $('#select-topic').val();
  $.getJSON("https://www.reddit.com/r/" + topic + ".json", function(data) {
    $.each(data.data.children, function(i, item) {
      $('<li><a href="' + item.data.url + '" target="_blank">' + item.data.title + '</a></li>').appendTo("#posts");
    });
  });
}

$(document).ready(function() {
  getRedditFeed();

  $('#select-topic').change(function() {
    $('#posts').html(''); // clear posts
    getRedditFeed();
  })
});