CODE EXAMPLE FOR JAVASCRIPT

javascript Why is this function working on second click only

let btn = document.getElementById('btn');
let hello = document.getElementById('hello');

function test() {
  if (hello.style.display !== 'none') {
    hello.style.display = 'none';
  } else {
    hello.style.display = 'block';
  }
}

btn.addEventListener('click', test)
<div id='hello'>
  hello
</div>

<div id='btn'>
  button
</div>