Part 3 - Modifying the onScroll method for handling the closeInvert state

Post.js

state = {
  dragProgress: 0,
  closeInverted: false,
};

onScroll = () => {
  /* same code */
  
  // handling close icon color
  const threshold = scrollTop / CLOSE_INVERTED_THRESHOLD;

  if (!this.state.closeInverted && threshold > window.innerHeight - 54) {
    this.setState({ closeInverted: true });
  } else if (
    this.state.closeInverted &&
    threshold <= window.innerHeight - 54
  ) {
    this.setState({ closeInverted: false });
  }
};