Set Inline Styles with the style Property

When I copied your code into the workspace, there were a few issues. I don't know if there was something not done in my workspace previously, but in my index.html, the button with the text "Update Heading" had an id of "btnmain" rather than having a class of "btn-main". Once I updated those to be the same as the video, I was getting "Uncaught TypeError: Cannot read properties of undefined (reading 'addEventListener')" on line 4. I removed the body element out of the addEventListener statement, and that seems to have resolved the issue. Here is the updated code:

const btnUpdate = document.querySelector('.btn-main');
const btnToggle = document.querySelector('.btn-toggle');

btnUpdate.addEventListener( 'click', () => { 
   const headline = document.getElementById('headline'); 
   const input = document.querySelector('.input-main'); 
   headline.className = 'grow'; 
   headline.textContent = input.value; 
   input.value = ''; 
});

btnToggle.addEventListener('click', () => {
  const listContainer = document.querySelector('.list-container');

  if (listContainer.style.display === 'none') { 
    btnToggle.textContent = 'Hide List';
    listContainer.style.display = 'block';
  } else {
    btnToggle.textContent = 'Show List';
    listContainer.style.display = 'none';
  }
});

By the way, when you post code, it makes it much easier for someone looking at it if you will post it with 3 backticks on a blank line before and after the code, so that it displays in code block like you wrote it. If you put js after the top 3 backticks, it will give syntax highlighting as well.