Smooth scroll from another pages by Javascript

Question

I created a smooth scroll with javascript. I made it ok for scrolling within page. But, when coming from another page, it goes to # position directory, then, starts animation. It's written in snippet if (urlHash) {} area.

I'd like the page to show up the top of body first, then, move to the link positions after 1 second, when coming from another page like clicking on index.html#block02.

I can't figure it out. Please help. Thanks a lot.

const anchors = document.querySelectorAll('a[href^="#"]');
const header = document.querySelector('header').offsetHeight;
const urlHash = location.hash;

for ( let i = 0; i < anchors.length; i++ ) {
  anchors[i].addEventListener('click', (e) => {
    e.preventDefault();

    const href= anchors[i].getAttribute("href");

    if (href !== '#top') {

      const target = document.getElementById(href.replace('#', ''));

      const position = window.pageYOffset + target.getBoundingClientRect().top - header;

      window.scroll({
        top: position,
        behavior: 'smooth'
      });

    } else {
      window.scroll({
        top: 0,
        behavior: 'smooth'
      });

    }
  });
}

window.addEventListener('DOMContentLoaded', (event) => {
  if (urlHash) {
    window.scrollTo({top:0});
    setTimeout(function () {

      const urlTarget = document.getElementById(urlHash.replace('#', ''));

      const urlPosition = window.pageYOffset + urlTarget.getBoundingClientRect().top - header;
      window.scroll({
        top: urlPosition,
        behavior: 'smooth'
      });
    }, 1000);
  }
});

header {position: fixed; width:100%; height: 100px; text-align:center; border-bottom:1px solid #ccc;}
div {height: 200vh;}
a {display: inline-block;}
main{padding-top: 100px;}

<header>header</header>
<main>
<a href="#block01">block01へ移動</a>
<a href="#block02">block02へ移動</a>

<div id="block01">block01</div>
<div id="block02">block02</div>

<a href="#top">topへ戻る</a>
</main>

Answer 1

Just reset scroll position at the top of your script:

setTimeout(() => { window.scrollTo(0, 0) }, 0) // Here

const anchors = document.querySelectorAll('a[href^="#"]');
const header = document.querySelector('header').offsetHeight;
const urlHash = location.hash;
// ...