var container = document.querySelector('container');

​

var max = 9;

var count = 0;

var dir = 1;

​

function updateCount() {

  if (count === max && dir === 1) {

    dir = -1;

    return;

  }

  if (count === 1 && dir === -1) {

    dir = 1;

    return;

  }

  count += dir;

}

​

function draw() {

  var html = '';

  for (var i = 0; i < count; i++) {

    html += '<column>'+(i+1)+'</column>';

  }

  container.innerHTML = html;

}

​

function anim() {

  updateCount();

  draw();

  setTimeout(anim, 300);

}

​

anim();