Part 2 - Setting onEnter function - referencing the preview node

Post.js

onEnter = () => {
  const { post } = this.props.route.data;

  this.preview = document.querySelector(`.preview[data-id="${post.id}"]`);  
  this.pageList = document.querySelector('.page-list');
  this.pageListStyler = styler(this.pageList);

  this.from = this.getPreviewStyleAndPosition();
};