修复 Vanilla JS Accordion 以一次展开一个选项卡

const acc = document.querySelector('#accordion');
if (acc === null) {

} else {
    let accordianHeaders = acc.querySelectorAll('header');
    let size = accordianHeaders.length;
    for (i = 0; i < size; i++) {
        accordianHeader = accordianHeaders[i];
        accordianHeader.setAttribute('class', 'toggle');
        accordianHeader.nextElementSibling.setAttribute('class', '');
        accordianHeader.onclick = function() {
            if (this.getAttribute('class') == 'toggle') {
                this.setAttribute('class', 'toggle-active');
                this.nextElementSibling.setAttribute("class", 'active');
                this.previousElementSibling.removeAttribute('class', 'active');
            } else {
                this.setAttribute('class', '');
                this.nextElementSibling.setAttribute('class', '');
            }
        }
    }
}

#accordion {
    padding-top: 25%;
    overflow: hidden;
    li {
        width: 100%;
        list-style-type: none;
    }
    header {
        display: flex;
        align-items: center;
        justify-content: flex-start;
        width: 100%;
        overflow: hidden;
        background-color: blue;
        max-width: 500px;
        padding: 10px;
    }
    i {
        width: 10%;
        color: white;
    }
    h3 {
        margin: 0;
        width: 90%;
        color: white;
    }

    article {
        max-height: 0;
        overflow: hidden;
        max-width: 600px;
        transition: 500ms max-height ease;
        &.active {
            max-height: 1000px;
        }
    }
    .toggle-active {
        i:before {
            content: "\f106";
        }
    }
}

<ul id="accordion">
    <li>
        <header>
            <i class="fa fa-angle-down"></i>
            <h3>List 1</h3>
        </header>
        <article>
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
        </article>
    </li>
    <li>
        <header>
            <i class="fa fa-angle-down"></i>
            <h3>List 2</h3>
        </header>
        <article>
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
        </article>
    </li>
    <li>
        <header>
            <i class="fa fa-angle-down"></i>
            <h3>List 3</h3>
        </header>
        <article>
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
        </article>
    </li>
</ul>

var lists = document.getElementsByTagName("header");

for(var i=0; i<lists.length; i++){

   lists[i].addEventListener("click", accordianHandler);
}

function accordianHandler(event){
  [...lists].map(o=> o.nextElementSibling.style.display = "none");
  
   event.target.parentNode.nextElementSibling.style.display = "block"

}

#accordion {
		padding-top: 25%;
		overflow: hidden;
		li {
			width: 100%;
			list-style-type: none;
		}
		header {
			display: flex;
			align-items: center;
			justify-content: flex-start;
			width: 100%;
			overflow: hidden;
			background-color: blue;
			max-width: 500px;
			padding: 10px;
		}
		i {
			width: 10%;
			color: white;
		}
		h3 {
			margin: 0;
			width: 90%;
			color: white;
		}

		article {
			max-height: 0;
			overflow: hidden;
			max-width: 600px;
			transition: 500ms max-height ease;
			&.active {
				max-height: 1000px;
			}
		}
		.toggle-active {
			i:before {
				content: "\f106";
			}
		}
	}

<ul id="accordion">
   <li>
      <header>
         <i class="fa fa-angle-down"></i>
         <h3>List 1</h3>
      </header>
      <article>
         <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
      </article>
   </li>
   <li>
      <header>
         <i class="fa fa-angle-down"></i>
         <h3>List 2</h3>
      </header>
      <article>
         <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
      </article>
   </li>
   <li>
      <header>
         <i class="fa fa-angle-down"></i>
         <h3>List 3</h3>
      </header>
      <article>
         <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
      </article>
   </li>
</ul>