setPosition = function(axis, $media, objectPosition) {
    var position, other, start, end, side;
    objectPosition = objectPosition.split(' ');

    if (objectPosition.length < 2) {
      objectPosition[1] = objectPosition[0];
    }

    /* istanbul ignore else */
    if (axis === 'x') {
      position = objectPosition[0];
      other = objectPosition[1];
      start = 'left';
      end = 'right';
      side = $media.clientWidth;
    } else if (axis === 'y') {
      position = objectPosition[1];
      other = objectPosition[0];
      start = 'top';
      end = 'bottom';
      side = $media.clientHeight;
    } else {
      return; // Neither x or y axis specified
    }

    if (position === start || other === start) {
      $media.style[start] = '0';
      return;
    }

    if (position === end || other === end) {
      $media.style[end] = '0';
      return;
    }

    if (position === 'center' || position === '50%') {
      $media.style[start] = '50%';
      $media.style['margin-' + start] = side / -2 + 'px';
      return;
    }

    // Percentage values (e.g., 30% 10%)
    if (position.indexOf('%') >= 0) {
      position = parseInt(position, 10);

      if (position < 50) {
        $media.style[start] = position + '%';
        $media.style['margin-' + start] = side * (position / -100) + 'px';
      } else {
        position = 100 - position;
        $media.style[end] = position + '%';
        $media.style['margin-' + end] = side * (position / -100) + 'px';
      }

      return;
    }
    // Length-based values (e.g. 10px / 10em)
    else {
      $media.style[start] = position;
    }
  }
Calculate & set object-position

@param {string} axis - either "x" or "y"
@param {node} $media - img or video element
@param {string} objectPosition - e.g. "50% 50%", "top left"