Array without duplicate values

by Génesis García Morilla

HTML

<div id="Set"></div>
<div id="filter"></div>

JavaScript

const array = [1, 2, 3, 3, 3, 2, 1];

// Array.from(iterableObj) = [...iterableObj] 
document.querySelector('#Set').innerHTML = [...new Set(array)];

// The filter strategy (easier to figure out)
document.querySelector('#filter').innerHTML = array
  .filter((elem, index) => index == array.indexOf(elem));